What People are Saying about Leo

Leo is revolutionary

“I am using Leo since a few weeks and I brim over with enthusiasm for it. I think it is the most amazing software since the invention of the spreadsheet.”—Anon.

“We who use Leo know that it is a breakthrough tool and a whole new way of writing code.”—Joe Orr

“I am a huge fan of Leo. I think it’s quite possibly the most revolutionary programming tool I have ever used and it (along with the Python language) has utterly changed my view of programming (indeed of writing) forever.”—Shakeeb Alireza

“Thank you very much for Leo. I think my way of working with data will change forever… I am certain [Leo] will be a revolution. The revolution is as important as the change from sequential linear organization of a book into a web-like hyperlinked pages. The main concept that impress me is that the source listing isn’t the main focus any more. You focus on the non-linear, hierarchical, collapsible outline of the source code.”—Korakot Chaovavanich

“Leo is a quantum leap for me in terms of how many projects I can manage and how much information I can find and organize and store in a useful way.”—Dan Winkler

“Wow, wow, and wow…I finally understand how to use clones and I realized that this is exactly how I want to organize my information. Multiple views on my data, fully interlinkable just like my thoughts.”—Anon

“Edward… you’ve come up with perhaps the most powerful new concept in code manipulation since VI and Emacs.—David McNab

“Leo is…a revolutionary step in the right direction for programming.”—Brian Takita

Leo is a showcase Python application

“Thanks for a wonderful program – everybody should be using it! It blows the socks off that Java Mind mapping software that won project of the month a while back on sourceforge!”—Derick van Niekerk.

“A few years back I would have said Zope was #1 Python showcase, but I agree 100% that Leo is tops now.”—Jason Cunliffe

“Leo is the most interesting Python project I know of…I see lots of stuff posted on the Daily Python page, but I usually yawn and come over to this forum to see what’s cooking.”—Anon

“What an original synthesis of different ideas, why can’t other Open Source projects change the way I think?”—Anon

Leo is fun, even addicting

“When first I opened Leo, it was out of curiosity. But having used it…I’ll never go back. They’ll have to pry Leo out of my cold, dead fingers! Seriously, it should be renamed ‘Crack Cocaine’ because it’s that addictive. I’m ready to start a 12-Step group.”—Travers A. Hough

“I feel addicted to programming again…in fact [Leo] has resurrected a dead project of mine :) The Outline has proven most liberating in terms of testing ideas out.”—Anon

“I have been absolutely seduced by Leo over the past few days. I tell you, I can not put it down. I feel like a kid with a shiny new bike…I’m already bursting with new ways I’d like to use the tool in the future.”—Lyn Adams Headley

Thanks for the great work–I love Leo!!!—Josef Dalcolmo

Leo has simplified updating and creating new scripts and .bats keeping similar information in the same place. there is almost an addictive withdrawal effect when I can complete an operation in so much less time with Leo & python than I had become used to.—Anon

Leo is my Favorites Mind Capsule ;-)

  • she can contain all kinds of my Works (novel, code, slides, documents…)
  • and she can magic record my chaos mind in same time and same place and NOT Disturb my working…
  • luvin Leo, make me freedom with chaos mind and structuring work export!
  • all my Slides is make with rst2s5
  • write rst in Leo
  • usage CLI tools generate html slides
  • easy, geek, and freedom!— 周琦 (Zoom.Quiet)

Leo is a flexible, powerful IDE

“[Leo] should either replace or greatly augment the development tools that I use.”—Zak Greant

“Leo is a marriage of outlining and programming. Pure genius. The main reason I am impressed with this tool is that it doesn’t affect your choice of tools. You can use whatever IDE for whatever language and switch back and forth between Leo and it.”—Austin King

“Leo is the best IDE that I have had the pleasure to use. I have been using it now for about 2–3 months. It has totally changed not only the way that I program, but also the way that I store and organize all of the information that I need for the job that I do.”—Ian Mulvany

“I only have one week of Leo experience but I already know it will be my default IDE/project manager…people complain about the lack of a project manager for the free/standard Python IDE’s like Idle. Leo clearly solves that problem and in a way that commercial tools can’t touch.”—Marshall Parsons

“I have been using Leo for about 3 weeks and I hardly use my other programming editor anymore…I find it easy and enjoyable to use. I plan to adopt it as my presentation tool for code reviews.”—Jim Vickroy

“I’m absolutely astounded by the power of such a simple idea! It works great and I can immediately see the benefits of using Leo in place of the standard flat file editor.”—Tom Lee

“I think you’re really showing what open source can do and your current trajectory puts you on track to kick Emacs into the dustbin of computing history.”—Dan Winkler

Leo is a superb outliner

“Word outlines are very useful. But Leo makes Word look like a clunky toy.”—Joe Orr

“Leo is an interactive editor for organizing text fragments hierarchically and sequentially into one or more files and hierarchical folders, without arbitrary limits on the number and size of text fragments and the depth of the hierarchy…”—Alex Abacus

“Leo reminds me a great deal of things I loved when I used Userland’s Frontier (an outlining cms with a native oodb) - but Frontier wasn’t hackable enough for me, and it wasn’t oriented towards coding…, and you couldn’t round-trip rendered pages (big Leo win). This is really a super tool - in a matter of days I’ve started to use it on all my projects and I still haven’t figured out how I lived without it.”—John Sequeira

“Leo is EXACTLY the kind of outliner I was looking for–fantastic job!”—Steve Allen

“Leo creates living documents. Ideas can be organized and reorganized gradually and then inserted into the appropriate place in a project. Outlines become fluid, allowing infinite depth and by using clones of nodes, arbitrary levels of complexity…[Other] outliners impose structure on documents…Leo is different. Instead of imposing structure, it allows you to impose your own infrastructure, and then be as creative as you want. This brings the necessary chaos of creativity to heel when it is time to produce the document. The node structure creates ultimate flexibility when it comes to ordering scenes in chapter. Say good-bye to copy and paste and hello to drag and drop.”—Chris George, in Thrive

Leo is an excellent PIM

“If you are like me, you have a kind of knowledge base with infos gathered over time. And you have projects, where you use some of those infos. Now, with conventional outliners you begin to double these infos, because you want to have the infos needed for the project with your project. With Leo you can do this too, but if you change text in one place IT IS UPDATED IN THE OTHER PLACE TOO! This is a feature I did not see with any other outliner (and I tried a few). Amazing! Leo directly supports the way I work!”—F. Geiger

“Another day, another breakthrough using Leo–now I realize Leo is the best URL bookmark manager there is. No more bookmarks menus or favorites lists inside the browser for me. With the @url directive I can just double click on the URL to open it in my browser. Leo lets me arrange the URLs in a hierarchy (or multiple hierarchies), attach notes to them, save clippings of things I read on the sites. It’s sooo much better than anything the browsers have built in and it lets me easily use different browsers on different platforms and different machines (try that with the browsers’ built-in bookmark managers).”—Dan Winkler

“I am an amateur photographer. I use plain old 35mm. film for my pictures. Over the weekend, I used Leo to organize my lists of pictures. It is quite helpful–I can have separate nodes for pictures I have enlarged, as well as pictures I have submitted to our local camera club. Thanks!”—Rich Reis

“Cloning is pure genius!… Leo’s cloning facility, allows me to create several views on the CFA course material. My main view follows the prescribed study guide. Another view is organized like the textbooks. Yet another gives me a glossary of terms. And when I’m done, I’ll have some nice libraries…I can re-use later in other projects.”—Michael Manti

Despite I am no programmer, I have been using Leo for some years now as my “Intelligent PIM” - I organize my (complex) life with Leo. Many thanks to Edward and others for the great application – vili <viljem.tisnikar@gmail.com>

I had used Leo for a long time as a PIM to track my work, but moved to emacs org mode for a period of time because of its explicit agenda and work tracking capabilities. But I went back to Leo because it seems more flexible when it comes to viewing various aspects of a project. For some recent performance data collection work, under one outline are the theory behind the project, the code (generation) for the project, the project web page (generated from an @rst node tree), and project deployment (little more than clicking a button). One can change focus from one aspect to another very quickly and use clones to really drill down into an area (for me it’s typically the code) when needed. Leo is an impressive tool, and I have only scratched the surface–Robert Shanley.

Leo is a superb documentation tool

“I’ve written documentation in WordPerfert, Ventura, Word, PageMaker, and FrameMaker and even though they create wonderfully looking and useful documents, they’ve never been able to do what I’ve been looking for. HTML, compiled help files, and later PDF came closer, but still not there…I think I’ve found it in Leo, a way to make a “living” document. A document built out of discrete parts that can be re-organized on the fly to meet the needs of a varying audience…I’ve already started converting the IT Procedures manual from Open Office to Leo because I know it’s going to be much more useful to me and anyone else…just the possibility of keeping system maintenance scripts in the IT manual is mind boggling.”—David Nichols

“With the help of the rst2 plugin, [Leo is] the best outliner I have yet encountered for writing the early stages of academic papers.”

“A Leo file is an ideal documentation tool, collecting the assorted readme.txt files, the comments from the source files…as well as the config files themselves.”—Kent Tenney

Leo simplifies the understanding of complex systems

“Just as structured programming reveals and disciplines the flow control of a program, [Leo] allows the designer to reveal and discipline structure at many layers simultaneously: data structures, object structure, entity-relationship structure, client-server structure, design pattern structure, temporal structure, project management structure, and any other structure relevant to the system.”—Steven P. Schaefer

“A funny observation with Leo is that when I ‘Leo-ise’ other people’s code, Leo makes the code’s structure so transparent that design faults become very quickly apparent. For example, maintenance pain caused by lack of factorization.”—David McNab

“Leo is a powerful tool for organizing text into tree structures, and for just generally attacking a number of problems from a tree-based perspective.”—Joe Orr

“I found this blog entry by someone (a talented former coworker of mine actually) complaining about some poorly written code she had to maintain: http://snippy.ceejbot.com/wiki/show/start/2003/01/29/001 She said: ‘You’d need a bulldozer to start refactoring it.’ That was my cue to write a long message explaining that there is indeed such a bulldozer and it’s called Leo. (You can see my message there as a reply to her original posting.) I gave her my recipe for how to get someone else’s messy, scary code into Leo and how to break it down into manageable chunks.”—Dan Winkler

“Ed, you continue to push the envelope. The amazing thing is that the footprint isn’t doubling every few months like it would be in another designer’s hands. Adding features by removing constraints, hot refactoring while adding unit tests. Forget the book. I would pay to see the movie.”

Leo is stable, well designed and well supported

“I am extremely impressed at how stable and useful Leo appears to be.”—Marcus A. Martin

“Leo is amazingly stable. Docs are often weak with Open Source Software. Not so Leo: Leo is unusually well documented.”—F. Geiger

“Leo is unimaginably useful and I always find new things it already knows(!) how to do. Indeed I am amazed by the never-ending resources and patience Edward is putting into it and its users community. Excellent.”—Gil Shwartz

I feel strongly that Ed Ream, our ever-patient, ever-productive Leo architect deserves a nomination [for the ActiveState OpenSource Award.] Among other reasons, for:

  • Delivering the first usable visual literate programming tool.
  • Adding a vast abundance of new features.
  • Making possible a previously unimaginable amount of leverage in code editing.
  • Eliminating vast amounts of menial programming labour.
  • Tirelessly and patiently supporting users, and catering to a wide range of feature requests.—David McNab

Steve Zatz explains why @clean changes everything

I just want to provide my own thoughts about the importance of @clean. I look at the posts in this group a fair amount because I find the discussion interesting but I had abandoned Leo as a day-to-day tool principally because of the sentinels in @file nodes. Even for solo projects, I just found them visually unappealing and beyond that occasionally confusing when I went to edit files with external editors. I would sometimes start a project in Leo, particularly if it was based on code I developed in the past using Leo, and then would use the old @nosent to save a version of the code without sentinels and then use my external editor of choice and not use Leo at all. I missed many of the features of Leo but just couldn’t get over the sentinel issue.

@clean really seems to solve all the issues that I had. In particular–and somehow this point doesn’t seem to me to have been emphasized enough–it seems to fully support organizer nodes. They are one of the great things about Leo–it’s happy to guess initially at what the structure of your program is but it’s completely up to you to determine the structure and the ability to do things like break up long methods, group like methods, group menu actions in GUI code, etc etc is one of the very cool things about Leo. My limited but growing experience with @clean’s handling of external changes has been mainly with incremental (as opposed to more sweeping) code changes, and the assignment of new lines is reasonable and you can always fix them it quickly if you don’t like how external changes have been handled.

There have been some posts about the recovered nodes, comparing the old and new nodes where there were external changes. I think it’s genius. As opposed to hoping that Leo has correctly incorporated external changes, it’s all there in case you want to take a closer look. Without this, I would just not have the confidence that external changes were being applied correctly and while you can always do a git diff, I am not looking to do that every time I change a file externally especially if I am not at the point where I am about to do a commit.

There has been some discussion of @auto v. @clean. Preference is obviously a matter of taste. I will say that for me the fact that node headlines are unaffected by external file changes is a feature not a problem since I place notes in the headlines that I want preserved when I edit files externally. Yes, if the node headlines are the method names then they won’t be updated if an external edit changes a method name but this was true of @file as well.

The ability to work on projects with people who don’t have Leo is obvious; one perhaps slightly less obvious benefit of no sentinels is that I suspect that the likelihood that someone will clone a git repository is reduced when that repository’s code is riddled with Leo sentinels (unless the potential cloner is a Leo loyalist). The one downside to no sentinels–there is no evidence that Leo is being used but I think that raises the broader question of marketing Leo, which I certainly believe will be aided significantly by being able to take advantage of Leo without sentinels in external files.— Steve Zatz

Quotes from Leo’s developers

“I would never again willingly program without Leo”—Edward K. Ream

From Terry Brown:

If you’re looking for an environment which includes a good editor and outliner and is completely scriptable / interactive / “live-code” in Python, then Leo wins hands down. Of course, it’s basically alone in this field, as far as I know, but I’m sure it would do well even if it wasn’t :-). Take out the Python part, and maybe they’re some others out there, but who’d want to take out the Python part :) I guess Emacs is sort of an environment like this, only in Lisp with a prehistoric GUI system.

Sometimes I’ve wondered why Leo seems to appeal to people who aren’t comfortable in Python, I think now it’s because they still recognize the value of an environment, and there’s just not much in this niche.

My feeling, talking generally and not about Leo in particular, is that while not everyone needs to be a “programmer”, everyone who uses computers would benefit from being able to interact with them with more of the flexibility and efficiency that comes with even relatively simple “scripting”, and less of the limitations that come with the “buy our latest product and you’ll be able to do anything you want with a click” view pushed by other suppliers of computing environments.

From Jacob Peck:

Leo’s impact on my life since I found it in January has been substantial.

Leo allows me to automate my life to a great extent. It is my to-do list, my personal assistant, my address book, my password log, my recipe archive, my rss feed reader (due to rss.py), and my favored editor. It partially powers my blog (along with git, ruby, and heroku), allowing me to create a new blog entry with one click and a bit of editing. Viewrendered (with markdown support!) has changed the way I write READMEs and blog posts. On top of all of that, it has allowed to me to organize several disparate tabletop game design projects I have going, as well as my numerous writing projects. Not to mention the impact it has on my ability to understand and decode large python projects!

But what really cinches all of this for me is how crazy extensible Leo is. Script buttons in particular are an integral part of my daily workflow, allowing me to transform my productivity over the last month…I’m now a thing-getter-doner, and I find much of it is due to the powerful core of Leo, plus scripting.py and todo.py.

From Ville M. Vainio:

The outliner format helps me organize/reorganize my thoughts gradually, instead of putting everything in the right place from the beginning. I write a lot of body text with few headlines, and Leo’s approach leaves lots of space for the body text and therefore suits my workflow. I find that I end up revisiting notes composed on Leo more often than notes slapped into tools like Evernote or random files in the file system.

With Leo, I can interleave “notes” (most of the content), generated files and even random data and python scripts to manipulate that data. I process this data in various tools, but Leo helps me group it together in “project specific” Leo files.

I know how to script the outline, so I can easily whip up different tools for my needs that deal with the headline structure directly.

From Terry Brown:

Why Leo? Because I have two nodes which were originally identical but are now different and I want to see the differences.

My outline loads a @file called ~/.leo/t/gen which contains a @button with several @rclick children for commonly used tasks. I add a new one, @rclick diff:

selected = c.getSelectedPositions()
open('/tmp/a_diff', 'w').write(selected[0].b)
open('/tmp/b_diff', 'w').write(selected[1].b)
import os
os.system("xxdiff /tmp/a_diff /tmp/b_diff &")

which is horrible for a number of reasons but also took only moments to write. And now, not only does this Leo session have a visual node diff capability, but also every future session which loads ~/.leo/t/gen.

When you can go from wanting to having a feature in less time than it takes to write an email about it - well, that’s “why Leo”.

Longer quotes…

Speed Ream’s slashdot article

August 28, 2002, on slashdot.

Hello, my full name is David Speed Ream. I am known as Speed to friends and enemies alike, but I gladly answer to David or most any other handle. I am an unabashed and biased fan of Leo, the fact that it was written by my brother Edward only slightly coloring my already colored glasses. I have been testing and using Leo in software production for over 4 years. My company currently has over 50,000 lines of code in over 100 source files that are written using Leo.

My comments are from two points of view, the first being software project manager for a complicated, multi-module software product, and the second being as a production line coder. For me, Leo’s greatest and only real drawback is the learning curve. This learning curve can be shallow if all that is required is that someone code using Leo. However, in our company we allocate 40 to 80 hours on top of the normal coding load for someone to come up to speed on Leo. The ROI (return on investment) is calculated by me to be on the order of 3 months. So if I hire a consultant for less than 3 months, I don’t teach him Leo, even though all source code in our company must reside in Leo files for the reasons I won’t go into now.

I consider that my coders are 15 to 30 percent more efficient in their daily operations than my competition’s people. This indefensible claim of mine is based on the changes in my productivity as Leo grew from a test document production tool to the primary production method for all our assembly, c and cpp source code.

Personally, I hate to deal with documentation when I write code, except:

  1. When I am first sitting down to solve a new problem. Then the documentation becomes quite long-winded and pontificatory, as if I were the only one on earth smart enough to solve the problem - or
  2. When I come back to code I or someone else has written and find the documentation insufficient to understand the code without study (seems to be most of the time).

So I do not require my engineers or myself to do a great job of documentation, nor do I use Leo for that purpose. Rather, it is Leo’s outlining and organizing ability, and Leo’s ability to create source files from within the outline that give me what I think is a tremendous competitive advantage. Each of my company’s products run on all versions of windows from Win 3.1 to XP. In our flagship software piece, there are ten main modules, and each module is maintained by one single Leo file. In the CODEC module, one Leo file named compress.leo organizes and creates seven .asm files, forty-four .c files, twenty .h files, two .def files, four .mak files, etc. etc. etc. This one file can be checked out from source code control and given to an engineer for the addition of a new feature.

In it are contained all the known issues for the CODEC, each issue arranged in its own clone section. One clone section groups together every routine, variable or type definition that must change between different versions of Windows. These sections could be from six different c source files, two assembly files, and eight .h files. Another clone section groups together those sections relating to memory problems, which change according to the memory configuration and TSR configuration (or lack thereof) on the target machine. Another clone section groups sections that fail (or don’t fail) if the routine in question was accidentally run during the dreaded ‘interrupt time’. Another clone section is a section containing clones, each of which is named after the major bug that was fixed when the engineer who fixed the bug grouped a bunch of routines, definitions, etc. together to fix the bug.

None of the above clone sections was ‘designed’ into the document. Just the opposite happens. When the codec was first written, there was just a single Leo file with a bunch of sections for each c routine or assembly module. As the product grew and was tested on various platforms, each failure of the module was organized into clones each time a failure was fixed. This is what I call “SELF DOCUMENTING CODE”. This has nothing to do with me sitting and documenting anything. Its just that the STRUCTURE of a bug fix (or product enhancement) lives on long after the coding is done, as long as no one is foolish enough to delete the cloned sections that ‘DOCUMENT’ what happened.

In actual practice, this organizational ‘history’ is so powerful that I can’t begin to describe it. A ‘REVERSE LEARNING CURVE’ happens when an engineer gets a Leo file that already has the ‘interrupt time sensitive’ routines grouped together by the last unfortunate soul who had to work on them. There may not be any more written documentation, but the knowledge contained in the structure can be breathtaking. It is certainly time saving. I find this particularly true in my own case. Often I’ll look at some code that seems totally unfamiliar and think ‘what idiot wrote this crap’. Then I’ll look at the version control comments and realize that I wrote the crap. Then for sure I know the documentation is non-existent, but the clones I used to develop it are still there, and they always serve to refresh my memory in an indescribable way.

Enough of this commentary, I just looked at the clock. Best wishes to anyone willing to try Leo for a week. I hope you will be glad you did.

Joe Orr

The Word outlines are very useful. But Leo makes Word look like a clunky toy.

#1 Reason would probably be clone nodes. One node can point to another. Another way of putting this is is that a leaf can be on more than one tree. For example, suppose you have a list of recipes. You simultaneously put a single recipe under multiple categories or even multiple hierarchies. You could put “3 bean enchilada” simultaneously under Recipes-Mexican and Food-Gas. Another example would be, if you are a biologist trying to decide under which genus to put a new species, you could put the species under two simultaneously. In effect, you can build a 3-D tree.

#2 Reason would probably be that Leo outlines can be embedded in external text files. So, a Leo outline is more than an outline, it is a meta-structure that can be added to another text without changing that text, but rather providing an external road map to the text. Microsoft Word has a text (xml) version with a commenting convention, so Leo can even be used to add outlines into Word docs, although it isn’t set up to do that now. For example, see http://www.3dtree.com/ev/e/sbooks/leo/sbframetoc_ie.htm In this case, the upper window of Leo is the meta-structure, and the bottom window is the file to which the meta-structure is being applied, viewed one node at a time.

I may not have made #2 very clear, but it is actually a very useful feature. It takes some getting used to before one sees all of the possibilities tho. One way to think of it is that Leo allows you to throw external documents into your outline, and yet the external document remains independent and can still be edited separately.

Some other cool things about Leo which Word doesn’t feature: 1. Pure xml output that is easy to transform into other formats (next version of Word will have true XML format, but not as easy to work with). One consequence of this is that Leo files can be transformed pretty easily to web pages with their outlining capability intact. 2. Easy to add features since is programmed in Python and open source. Maybe your average user can’t start hacking on it, but a surprising amount can be tacked on… 3. Free, opensource, multi-platform 4. Leo is scriptable with Python. It should be possible to build a Tickler into Leo using Python scripting, for example.

Dan Winkler

First of all, kudos to you for the excellent progress you’ve been making with Leo. I upgraded today after about three months of using and older version and I was thrilled to see all the great improvements that have happened so fast. I especially love the ability to go to next clone. I think you’re really showing what open source can do and your current trajectory puts you on track to kick Emacs into the dustbin of computing history.

So today I copied all my data (personal information manager and project management stuff) out of my old outliner (ThoughtManager, which syncs with and runs on the Palm) and put it into Leo. It took me hours to do it and then to rearrange it the way I really wanted it. But having the ability to make clones and have different ways to view my data is, as you know, fabulous. In my case, for personal information and project management things, I used the flexibility of clones to allow me to see my data in several different views: 1) by project, the logical hierarchical breakdown by topic, 2) by person, so whenever I’m talking to someone I can easily see all the pending items related to them which may be spread over multiple projects, 3) by priority, so I can see what needs to get done sooner and what can wait for later and, 4) a special case of priority called “Today” for the things I’m going to focus on in the coming hours.

Now here’s why I don’t miss the ability of my old outliner to sync the entire outline with the Palm. It turns out the main thing I really want in the Palm is the top category “Today” so all I have to do is have Leo flatten that one heading into a text file (and it kindly remembers the name and directory of the file I used last time) and then I’m done because I’ve told the Palm Hotsync manager that that file should be sent to Palm memo pad every time I sync. The Palm Hotsync manager does a nice job of sending a text file to the Palm memo pad and even breaks the file up into multiple memo records if it’s too big to fit in just one. So that gives me enough to be able to browse (or full text search) the small amount of data that I really want right inside my Palm (which is also my cell phone). Quick and dirty but it works.

For times when I want my whole outline with me, Leo wins again because thanks to its cross platform nature I can take my whole outline with me on my Mac iBook, even though I usually edit it on a Windows PC (which is the only kind of machine my old outliner would run on). Quite frankly, although my old outliner was able to shoehorn the whole thing into my palm/cellphone, it was a pain to access it on the small screen and slow processor. Now when I anticipate I’ll need the whole thing, for example when I’m going to a meeting, I can put it on my Mac iBook (under X and Fink for now until Python can do it native under Aqua) and have real, full access to it all.

I think now in addition to being great for programming Leo is also a great PIM. Being able to flatten a strategically chosen portion of the outline into a known file name that the Palm sync manager has been told to send to the Palm on every sync does the trick for me. I wonder if you would consider something like an @flatten directive so I can have that done automatically for me every time I save my outline? For now it’s up to me to flatten the node I want manually, although once I’ve done that the transfer to the Palm is automatic.

You’re my hero! Thank you so much.

Dan Winkler 2

Another day, another breakthrough using Leo–now I realize Leo is the best URL bookmark manager there is. No more bookmarks menus or favorites lists inside the browser for me. With the @url directive I can just double click on the URL to open it in my browser. Leo lets me arrange the URLs in a hierarchy (or multiple hierarchies), attach notes to them, save clippings of things I read on the sites. It’s sooo much better than anything the browsers have built in and it lets me easily use different browsers on different platforms and different machines (try that with the browsers’ built-in bookmark managers).

When using Leo as a project manager and personal information manager as I do I can heavily annotate every task and project with helpful and relevant URLs. And since URLs can be of the file:// form, they’re not just for web pages or HTML documents; I can link to any file on my disk of any type to be opened by any program.

Leo is a quantum leap for me in terms of how many projects I can manage and how much information I can find and organize and store in a useful way. I’m a data-mining army of one now and the web is my playground. Every time I find a web page that has interesting links to others, those links get stored in my Leo outline too, right where I can find them and make practical use of them. I can easily accept dozens of valuable links every day and integrate them into what I’m doing in a way that I’m confidant they won’t get lost or forgotten. Before I always used to get bogged down by the difficulty of managing bookmarks inside the browser. But now I’m no longer the victim of information overload buried in the knowledge landslide of the Internet; instead I’m the professional strip miner with the world’s biggest bulldozer. I eagerly plunge into mountains of data and emerge with all the valuable information nuggets neatly stored and organized. And my storehouse of knowledge is a flexible thing where I can reorganize and prioritize and massage the data to my heart’s content as I learn more about it and decide to use it in different ways for different purposes. It’s the difference between the pick axe and the steam shovel for me.

Dan Winkler 3

This year my accountant is getting a beautiful printout generated by LaTeX and Leo. I have a complicated tax situation this year, but I got it all laid out and organized in Leo. Then I had each of the nodes that had something my accountant needs to see write the data out to a file in the form a LaTeX table.

Sometimes a row of a table would have a result that was calculated by adding up a list of numbers. For that I used the modern day equivalent of an adding machine paper tape–I stored a lisp s-expression in a Leo comment. I like s-expressions for this because once I put the opening “(+” on one line and the closing “)” on another line, I can fill in additional numbers just by typing them and can even annotate them with comments. So in the middle of generating a LaTeX file I might have something like this:

1165.26 1823.70 ; May 2002
123.38 ; June 2002
13.50 ; July 2002
13.21 ; October 2002
55.25 ; November 2002

That’s an annotated record of how I arrived at the number the accountant will actually see. I can just paste it into any lisp or scheme interpreter and get the total. Adding additional numbers is easy.

For next year, I think I might take this a step further. What I did this year is good for adding up numbers to get a total for one row of a LaTeX table. But it turns out I’d also like some more processing done on those tables (which I had to do by hand this time–I’d like the rows sorted in reverse order by magnitude (so that the big numbers jump out at you from the start of the tables) and I’d like a total of all the rows in the table. So I think next year, instead of having an s-expression that computes the total of one row for me, I think I’ll use s-expressions that generate whole tables, formatted for LaTex, from the underlying data. So I’m thinking next year my s-expressions might look more like this:

(table "Widget Related Expenses"
    ("widget insurance" (+
                    1165.26 1823.70 ; May 2002
                    123.38 ; June 2002
                    13.50 ; July 2002
                    13.21 ; October 2002
                    55.25 ; November 2002
     ("widget shipping" (+
                    472.15 651.94 ; May 2002
                    54 ; June 2002
     ("widget cleaning" (+
                    165.26 183.70 ; May 2002
                    123.38 ; June 2002
                    13.50 ; July 2002
                    13.21 ; October 2002
                    55.25 ; November 2002

The job of that “table” function would be to return the LaTeX code needed to display a table with the category names and values, sorted descending by magnitude, with the total displayed. It’s sort of a poor man’s way of doing a spreadsheet inside Leo and then making it look great using LaTeX. The idea would be as I wanted to add more data, I’d add it to the s-expression and then reevaluate the whole thing by pasting it into a lisp interpreter and then copying the result back into the same Leo node for LaTeX to process.—Dan

Steve Litt

“Not sure why you said ‘you can specify a computer program as an outline like thing in an outliner like setting.’ Why not just say, ‘write a computer program in an outline?’ Is there some nuance I am missing?”—EKR

There are probably a million reasons I said it like that, but I think the main one is my ever present, brightly burning belief that a program should be designed before its coded. Remember those guys, back in the day, who after receiving their programming assignment, would go to the keyboard and start pounding out C code? Remember their finished product? Remember how long it took them to finally complete the project?

Meanwhile, when receiving an assignment, I’d spend hours to days with a bunch of paper, drawing diagrams. By the time I sat down at the terminal, I knew my data structures and algorithms. The hours to days head start of the “start coding immediately” guys evaporated because for me, coding was just a secretarial task, and I was required to do less refactoring, or even worse, kludging. Later, sometimes I’d substitute an outliner for the diagrams on paper; in the days of functional decomposition, an outliner was the perfect fit.

Back to your question: If all I needed to do was write a program, I’d just sit down at a computer and start pounding out C or Python or Lua or whatever. But that’s not my style. I need to design a program, and after all, a design is just a specification of how the program is going to be written.

So it seems to me that I design the program on Leo, and then, when the time comes, I flip a switch and Leo writes the program for me. That’s how I’d view what I’ve heard about Leo.

Dave Williams

I am a microbiologist mostly analyzing large numbers of bacteria genomes for which I use almost entirely Python tools. A couple of years ago while working at Yale University I gave Leo go for writing Python and organizing my notes with.

Not only do I now use Leo is a central repository for scripts I write as I explore the data, generate plots, start analyses with third party applications etc., but also for storing and organizing ideas for research and notes parsed out of PDFs of academic papers. And that’s just for work!

I have a calendar, addresses all my general PIM-type info, and notes for any project I’m tinkering with. In short whether I’m at work or play Leo is usually involved :-)

John Lunzer

A new user recently said to me, “Leo is powerful and flexible–and complex and bewildering”. This is true. I believe it is always the goal of developers to make their software less complex and bewildering but keep in mind that Leo has been in development for over 20 years…This puts it right up there with Vim and Emacs in terms of maturity. My own experience with Vim and Emacs have been quite similar to my experience with Leo. All three are powerful and flexible and complex and bewildering in their own right.

I believe with tools of this weight and impact, there will always be an investment in learning them. They’re all vast forests of features filled with hidden treasures and in the case of each of them he/she that invests in the tool will be rewarded for their effort. It is, however, the responsibility of the community (led by the developers) to help make that treasure hunt as enjoyable and adventurous as possible, as any good treasure hunt should be.

And this is where Leo does not falter, in the helpfulness of its community (small though it may be). I will reiterate what Edward has said many times, do not struggle on your own if you are lost, confused, or bewildered. Please ask questions. If the documentation or examples do not meet your needs, please ask questions. In my own experience as a once new user (though there may be the occasional disagreement) you will not be chided, scorned, or belittled but will be met with more even more help than you originally asked for. – John Lunzer <lunzer@gmail.com>

John Lunzer 2

Lately I’ve been thinking about programming in general. My thoughts have centered on the limits of the human brain to understand computer programs. This was triggered by watching Inventing on Principle. It’s a daunting multifaceted concept which I’m sure people spend their entire lives pondering.

Most recently I’ve been focusing on one facet, abstraction and program “units”. I define a “unit” as a part of the program that is considered a piece onto itself which can be labeled and referred to as a whole. Perhaps, as a daily Leo user, this is easy to think about because Leo does its best to coerce programmers and programs into looking at programming through this lens.

Most tools do not ignore this concept all together. Most programming environments have some sort of “outline” window which allows you to view the structure of a program at a higher level. As I have experienced it this “outline” view is always dictated by the features of a language (ex. outline divided up at module, class, function levels). In addition most tools incorporate “code folding” to help a programmer focus on language specific programming units (again, ex. folding at class and function definitions).

Leo takes this concept to its limit. Leo offers language agnostic abstraction at arbitrary levels. It allows a programmer to structure their program outside of the confines of the programming paradigms of the language they’re programming in. Of course it still helps to use the language specific “units” as a guide, in fact this is what Leo does upon import to create an initial outline structure from programs originating outside of Leo.

I can’t ignore the freedom of arbitrary abstraction, and I’ve come to rely upon it so much that I struggle to use non-Leo environments. It is well known that the human brain has a limited working memory. The act of programming stretches working memory to it’s limit. Leo provides an environment in which a program can seamlessly be restructured to fit within the bounds of a programmers individual working memory.

I realize this is a “why” and not a “how” and that this doesn’t help anyone get better acquainted with Leo. But, as a programmer if you’ve ever felt frustrated with the organizational constructs of the language you’re working in you might be surprised to realize that after using Leo it wasn’t the language that was the problem, but a lack of tools to organize your programs in a way that makes sense to you.

Adrian Calvin

I thought I would write my own testimonial. I don’t ever do this, as I often roll my eyes at testimonials, but my enthusiasm is at such a degree about Leo, that I must give “props” where props are due.


The Beginning: Coming from being a Java professional in the early aughts, I was used to Netbeans. It was fine I guess. A few years later I decided I wanted to be a web developer.

Why I sought out a new editor: I wanted something extensible in FULL. I wanted to make it my own. It is like your home. You move in, it is up to you to make it your “HOME”. So is an editor. You spend all of your time with it. It must be YOURS I figure. Comfy like a pair of old shoes.


Ultra-Edit: This was my first non-ide, IDE. No disrespect to UltraEdit, I am sure it has many awesome features I never used. I never really got the chance. I wanted something lightweight and soon found Scite around 2006.

Notepad++: Eventually I found Notepad++ (which I still think is awesome, and would recommend to anyone). I have been using it for 8 years, and I still do use it occasionally. Mostly because I am still getting used to Leo.


I am at an age now, and a point in my career where I want to make my life (and job) as simple as possible. Leo helps me do that. It is hard to explain–the outlining gives the ability to mix thoughts with code–even life with code, in a very intuitive fashion. Perhaps this is “literate programming”. I don’t know. They never mentioned that term in my CS classes. Whatever it is, I like it.

Side benefit–my code has never been so well formatted and documented!

The thing I personally love most

As I alluded to, so much ability to extend. At work, I work on what my boss wants, but at home, I spend most of my time extending Leo. I have never seen an editor so easy to extend, and believe me, I have evaluated at least 20 editors in the past 5 months.

That’s the thing–anything I want to work a different way, or anything I want to be better, I can do it on my own. I don’t have to submit a request. If I at least have enough curiosity to google or ask for a bit of help, I can make it what I want.

You name it.

  • If I would like the log to work differently, or create my own output pane: no problem.
  • If I want to add PHP Unit tests to the menu, no problem.
  • If I want to make a personal organizer, mixed in with my work flow, no problem.
  • If I want to have my python, PHP code, journal, all integrated together so that everything makes sense from 20,000 feet, no problem.
  • If I want to change the entire look and feel…and I mean EVERYTHING…not just some things, no problem.
  • If I want to be able to easily explain the code to a non-technical colleague, no problem. The outline can be followed by anyone with some degree of intelligence.

You get the idea…

And for me, that means everything.

Why Leo is noteworthy

Leo is a superb tool for understanding, studying and organizing any kind of complex data, including computer programs. The first great Aha in Leo’s history was that webs (literate programs) are outlines in disguise. Leo’s importers (@auto) make it easy to studying other people’s programs. Leo’s always-present outline structure clarifies overall program structure and makes many kinds of comments unnecessary.

Leo is also a superb browser for code and data. Unlike many other folding editors, Leo remembers which nodes were expanded when you last saved an outline. This is surprisingly important. And Leo’s clones let you organize any data as you want, even if all folds are collapsed.

Leo is a uniquely powerful scripting environment. This power comes from three sources: Leo’s API, Leo’s ability to compose scripts from outlines and Leo’s underlying data structure, a Directed Acyclic Graph, the basis for Leo’s clones.

Leo’s API consists primarily of generators, such as c.all_positions(), p.self_and_subtree(), etc. and properties, such as p.b, p.h, p.gnx and p.v.u. Leo’s API makes it trivial to write scripts to access or change any node. AFAIK, these capabilities are unique. Simulating them in vim or Emacs is possible, but so is simulating Python’s capabilities in C…

Afaik, no other scripting environment allows you to compose scripts from outlines. @file, @clean, @auto, @others and section references and definitions make this possible. Section references and definitions are modeled on the noweb language, but all of Leo’s script composition features are fully integrated into Leo’s outline structure.

Leo’s outline nodes have headlines (p.h) and body text (p.b) and extensible information (p.v.u). Headlines are descriptions (meta-data) of the data in p.b and p.v.u. Scripts can rapidly discover and categorize data using metadata. Leo’s @ convention for headlines (@clean, @file, @auto, @html, etc.) show how extensible this node typing is.

So much for the theory. The following also are important in practice:

  • Native scripting in Python, with full access to all of Leo’s sources.
  • Leo’s plugin architecture.
  • Leo’s rst3 command, vim, xemacs and ILeo (IPython bridge), and leoBridge module.
  • Leo’s minibuffer commands, borrowed shamelessly from Emacs.
  • @test and @suite: Leo’s outline-oriented unit testing framework.
  • @button: bringing scripts to data.
  • Leo’s outline-oriented directives.

The invention/discovery of @clean earlier this year completes Leo is some sense.

Acknowledgements: Working with Leo’s community of Leo’s developers and users has been a great pleasure for over 20 years. My only regret is that Bernhard Mulder and Bob Fitzwater are no longer with us. Both made essential contributions. Bob Fitzwater was my mentor. He gently pushed me to consider design, not just “bit twiddling”. Bernhard Mulder contributed two of the most important elements of Leo: Leo’s traversers (generators) and the original @shadow algorithm. Neither @clean nor the revised Mulder/Ream algorithm could possibly have happened without him. I miss both these great thinkers. Both would have been proud of what they helped create.

A successful software tool is one that was used to do something undreamed of by its author.’ – Stephen Johnson

Leo is a wild success on this score. I foresaw none of these developments 20 years ago: Leo’s minibuffer, @button, @test, @auto, @clean, Leo’s plugin architecture, the rst3 command, the Leo bridge and the IPython bridge. Surely many other features and uses could be added. None of these would have happened without Leo’s community of brilliant people. These features create the Leonine world. Who knows what will be the result…

Edward K. Ream

Offray Luna Cárdenas

This idea of an always-present outline has been key to me for organizing writings. Some coworkers have found in the past that this helps them when we’re correcting their text.

> Leo’s clones let you organize any data as you want, even if all folds are collapsed.

For me this is the most powerful but misunderstood feature of Leo. Most of the people which compares it with other IDE rant about why Leo doesn’t works more automatically imposing structure, but in Leo you’re in charge. You impose infrastructure…

For me the second main insight of Leo (besides emergent always present tree structure on almost any file) was to have a tree that is a programmable structure that can be understood and changed by any node inside that tree. I think that Leo brings structure and self-referentiality to the dumb flat file word. So you can create a tree from one (or several) files, deconstruct and reconstruct it they way you want and automatize the way in behaves and talks with the external world…The more I start to focus on interactive writing and going away of the unix inspired OS world, the more the second insight become important to me. I didn’t need to deconstruct/reconstruct or impose structure over flat files but to use outlining for structure thought by (interactive) writing and I need the outline be a fully programmable object. That’s the essence of most of my Leo experience…

Thanks for Leo and all the key inspiration it brings. And, as always, thanks to the Leo community for the food for thought.

Speed’s comments

My only input is what makes Leo so special to me.

After learning just a few things about Leo, and after replacing section references mostly with @others, writing code becomes a game rather than a chore.

As soon as an idea becomes complicated, I add a new @others, and break down the complication into chunks until all the complications are now simple.

I’ll typically clone that section an the bottom of the outline, then add enough logic at a parent level so that the complication can be tested with control B.

This is my backward implementation of unit testing. This kind of ‘unit testing’ never has to be refactored when the code is (invariably) improved.

The cloned ‘test piece’ can be relegated to a testing section, and the new chunks subsequently cloned into whatever structure make real sense for the project.

In practice, this is just fun for me.

Coding without Leo is not really fun any more. I recently finished a c++ socket server using Microsoft’s Visual Studio, in concert with someone who didn’t have Leo. Microsoft’s tools are great, and the project went off without a hitch, but the fun was just plain gone.

Anyway, thanks for the great perspective on Leo.