# Scheme

## Which language is best, C, C++, Python or Java?

My current answer is: Scheme ☺ It gives me a large degree of freedom to explore ways to program which were much harder hard to explore in Python, C++ and Java. That’s why I’m currently switching from Python to Scheme.1

But depending on my current step on the road to improve my skills2 and the development group and project, that answer might have been any other language — C, C++, Java, Python, Fortran, R, Ruby, Haskell, Go, Rust, Clojure, ….

1. Apprenticeship Patterns — Guidance for the Aspiring Software Craftsman

## Going from Python to Guile Scheme - a natural progression

Python is the first language I loved. I dreamt in Python, I planned in Python, I thought I would never need anything else.

- Free: html | pdf
- Softcover: 14.95 €
with pdf, epub, mobi

## Exact Math to the rescue - with Guile Scheme

I needed to calculate the probability that for every freenet user there are at least 70 others in a distance of at most 0.01. That needs binomial coefficients with n and k on the order of 4000. My old Python script failed me with an `OverflowError: integer division result too large for a float`. So I turned to Guile Scheme and exact math.

## Recursion wins!

I recently read the little schemer and that got me thinking about recursion and loops.

After starting my programming life with Python, I normally use for-loops to solve problems. But actually they are an inferior mechanism when compared to recursion, if (and only if) the language provides proper syntactic support for that. Since that claim pretty much damns Python on a theoretical level (even though it is still a very good tool in practice and I still love it!), I want to share a simplified version of the code which made me realize this.

## Installing GNU Guix 0.6, easily

Org-Source (for editing)

PDF (for printing)

“Got a power-outage while updating?
No problem: Everything still works”

GNU Guix is the new functional package manager from the GNU Project which complements the Nix-Store with a nice Guile Scheme based package definition format.

What sold it to me was “Got a power-outage while updating? No problem: Everything still works” from the Guix talk of Ludovico at the GNU Hacker Meeting 2013. My son once found the on-off-button of our power-connector while I was updating my Gentoo box. It took me 3 evenings to get it completely functional again. This would not have happened with Guix.

Update (2014-05-17): Thanks to zerwas from IRC @ freenode for the patch to guix 0.6 and nice cleanup!

## Intro

Installation of GNU Guix is straightforward, except if you follow the docs, but it’s not as if we’re not used to that from other GNU utilities, which often terribly short-sell their quality with overly general documentation ☺

So I want to provide a short guide how to setup and run GNU Guix with ease. My system natively runs Gentoo, My system natively runs Gentoo, so some details might vary for you. If you use Gentoo, you can simply copy the commands here into the shell, but better copy them to a text-file first to ensure that I do not try to trick you into doing evil things with the root access you need.

In short: This guide provides the First Contact and Black Triangle for GNU Guix.

## Let-Rekursion ist toll!

English alternative: My favourite Scheme feature: named let. With more implementation details.

Code-Snippets:

Ich habe dank Pythonista in Scheme-Land von Let-Rekursion gelesen. Bis vorgestern fand ich sie noch sinnlos kompliziert.

Das hat sich alles geändert, als ich wirklichen Code damit geschrieben habe - zum Beispiel die Fibonacci-Folge (syntax: wisp1 für Guile Scheme2) (eigentlicher Augenöffner):

```define : fib n
let rek : (i 0) (u 1) (v 1)
if : >= i : - n 2
. v
rek (+ i 1) v (+ u v) ; else
```

Um Let-Rekursion zu beschreiben, werde ich diese Funktion jetzt zu einer Schleife in Python transformieren und mich zu immer eleganteren Formulierungen vortasten, bis ich wieder bei dem gerade gezeigten Code bin; dann aber mit Hintergrundwissen darüber, wodurch er elegant wird, mit dem Verständnis, was genau er tut, und mit einem Gefühl dafür, wie viel diese Eleganz ausmacht - und warum sie erstrebenswert ist.

## wisp: Whitespace to Lisp

New version: draketo.de/software/wisp

» I love the syntax of Python, but crave the simplicity and power of Lisp.«

```display "Hello World!" ↦ (display "Hello World!")
```
```define : factorial n     (define (factorial n)
if : zero? n       ↦     (if (zero? n)
. 1                      1
* n : factorial {n - 1}  (* n (factorial {n - 1}))))
```

## Wisp basics

»ArneBab's alternate sexp syntax is best I've seen; pythonesque, hides parens but keeps power« — Christopher Webber in twitter, in identi.ca and in his blog: Wisp: Lisp, minus the parentheses
♡ wow ♡
»Wisp allows people to see code how Lispers perceive it. Its structure becomes apparent.« — Ricardo Wurmus in IRC, paraphrasing the wisp statement from his talk at FOSDEM 2019 about Guix for reproducible science in HPC.
☺ Yay! ☺
```with (open-file "with.w" "r") as port
format #t "~a\n" : read port```
Familiar with-statement in 25 lines.

Update (2020-09-15): Wisp 1.0.3 provides a `wisp` binary to start a wisp repl or run wisp files, builds with Guile 3, and moved to sourcehut for libre hosting: hg.sr.ht/~arnebab/wisp.
After installation, just run `wisp` to enter a wisp-shell (REPL).
This release also ships wisp-mode 0.2.6 (fewer autoloads), ob-wisp 0.1 (initial support for org-babel), and additional examples. New auxiliary projects include wispserve for experiments with streaming and download-mesh via Guile and wisp in conf:
`conf new -l wisp PROJNAME` creates an autotools project with wisp while `conf new -l wisp-enter PROJAME` creates a project with natural script writing and guile doctests set up. Both also install a script to run your project with minimal start time: I see 25ms to 130ms for hello world (36ms on average). The name of the script is the name of your project.
To test wisp v1.0.3, install Guile 2.0.11 or later and bootstrap wisp:

`wget https://www.draketo.de/files/wisp-1.0.3.tar_.gz; tar xf wisp-1.0.3.tar_.gz ; cd wisp-1.0.3/; ./configure; make check; examples/newbase60.w 123`

If it prints 23 (123 in NewBase60), your wisp is fully operational.
If you have additional questions, see the Frequently asked Questions (FAQ) and chat in #guile at freenode.
That’s it - have fun with wisp syntax!

Update (2019-07-16): wisp-mode 0.2.5 now provides proper indentation support in Emacs: Tab increases indentation and cycles back to zero. Shift-tab decreases indentation via previously defined indentation levels. Return preserves the indentation level (hit tab twice to go to zero indentation).
Update (2019-06-16): In c programming the uncommon way, specifically c-indent, tantalum is experimenting with combining wisp and sph-sc, which compiles scheme-like s-expressions to c. The result is a program written like this:
```pre-include "stdio.h"

define (main argc argv) : int int char**
declare i int
printf "the number of arguments is %d\n" argc
for : (set i 0) (< i argc) (set+ i 1)
printf "arg %d is %s\n" (+ i 1) (array-get argv i)
return 0 ;; code-snippet under GPLv3+```
To me that looks so close to C that it took me a moment to realize that it isn’t just using a parser which allows omitting some special syntax of C, but actually an implementation of a C-generator in Scheme (similar in spirit to cython, which generates C from Python), which results in code that looks like a more regular version of C without superfluous parens. Wisp really completes the round-trip from C over Scheme to something that looks like C but has all the regularity of Scheme, because all things considered, the code example is regular wisp-code. And it is awesome to see tantalum take up the tool I created and use it to experiment with ways to program that I never even imagined! ♡
TLDR: tantalum uses wisp for code that looks like C and compiles to C but has the regularity of Scheme!
Update (2019-06-02): The repository at https://www.draketo.de/proj/wisp/ is stale at the moment, because the staticsite extension I use to update it was broken by API changes and I currently don’t have the time to fix it. Therefore until I get it fixed, the canonical repository for wisp is https://bitbucket.org/ArneBab/wisp/. I’m sorry for that. I would prefer to self-host it again, but the time to read up what i have to adjust blocks that right now (typically the actual fix only needs a few lines). A pull-request which fixes the staticsite extension for modern Mercurial would be much appreciated!
Update (2019-02-08): wisp v1.0 released as announced at FOSDEM. Wisp the language is complete:
```display "Hello World!" ↦ (display "Hello World!")```
And it achieves its goal:
“Wisp allows people to see code how Lispers perceive it. Its structure becomes apparent.” — Ricardo Wurmus at FOSDEM
Tooling, documentation, and porting of wisp are still work in progress, but before I go on, I want thank the people from the readable lisp project. Without our initial shared path, and without their encouragement, wisp would not be here today. Thank you! You’re awesome!
With this release it is time to put wisp to use. To start your own project, see the tutorial Starting a wisp project and the wisp tutorial. For more info, see the NEWS file. To test wisp v1.0, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-1.0.tar.gz; tar xf wisp-1.0.tar.gz ; cd wisp-1.0/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
If you have additional questions, see the Frequently asked Questions (FAQ) and chat in #guile at freenode.
That’s it - have fun with wisp syntax!
Update (2019-01-27): wisp v0.9.9.1 released which includes the emacs support files missed in v0.9.9, but excludes unnecessary files which increased the release size from 500k to 9 MiB (it's now back at about 500k). To start your own wisp-project, see the tutorial Starting a wisp project and the wisp tutorial. For more info, see the NEWS file. To test wisp v0.9.9.1, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.9.1.tar.gz; tar xf wisp-0.9.9.1.tar.gz ; cd wisp-0.9.9.1/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2019-01-22): wisp v0.9.9 released with support for literal arrays in Guile (needed for doctests), example start times below 100ms, ob-wisp.el for emacs org-mode babel and work on examples: network, securepassword, and downloadmesh. To start your own wisp-project, see the tutorial Starting a wisp project and the wisp tutorial. For more info, see the NEWS file. To test wisp v0.9.9, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.9.tar.gz; tar xf wisp-0.9.9.tar.gz ; cd wisp-0.9.9/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2018-06-26): There is now a wisp tutorial for beginning programmers: “In this tutorial you will learn to write programs with wisp. It requires no prior knowledge of programming.”Learn to program with Wisp, published in With Guise and Guile
Update (2017-11-10): wisp v0.9.8 released with installation fixes (thanks to benq!). To start your own wisp-project, see the tutorial Starting a wisp project. For more info, see the NEWS file. To test wisp v0.9.8, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.8.tar.gz; tar xf wisp-0.9.8.tar.gz ; cd wisp-0.9.8/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2017-10-17): wisp v0.9.7 released with bugfixes. To start your own wisp-project, see the tutorial Starting a wisp project. For more info, see the NEWS file. To test wisp v0.9.7, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.7.tar.gz; tar xf wisp-0.9.7.tar.gz ; cd wisp-0.9.7/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2017-10-08): wisp v0.9.6 released with compatibility for tests on OSX and old autotools, installation to `guile/site/(guile version)/language/wisp` for cleaner installation, debugging and warning when using not yet defined lower indentation levels, and with `wisp-scheme.scm` moved to `language/wisp.scm`. This allows creating a wisp project by simply copying `language/`. A short tutorial for creating a wisp project is available at Starting a wisp project as part of With Guise and Guile. For more info, see the NEWS file. To test wisp v0.9.6, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.6.tar.gz; tar xf wisp-0.9.6.tar.gz ; cd wisp-0.9.6/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2017-08-19): Thanks to tantalum, wisp is now available as package for Arch Linux: from the Arch User Repository (AUR) as guile-wisp-hg! Instructions for installing the package are provided on the AUR page in the Arch Linux wiki. Thank you, tantalum!
Update (2017-08-20): wisp v0.9.2 released with many additional examples including the proof-of-concept for a minimum ceremony dialog-based game duel.w and the datatype benchmarks in benchmark.w. For more info, see the NEWS file. To test it, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.2.tar.gz; tar xf wisp-0.9.2.tar.gz ; cd wisp-0.9.2/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2017-03-18): I removed the link to Gozala’s wisp, because it was put in maintenance mode. Quite the opposite of Guile which is taking up speed and just released Guile version 2.2.0, fully compatible with wisp (though wisp helped to find and fix one compiler bug, which is something I’m really happy about ☺).
Update (2017-02-05): Allan C. Webber presented my talk Natural script writing with Guile in the Guile devroom at FOSDEM. The talk was awesome — and recorded! Enjoy Natural script writing with Guile by "pretend Arne" ☺

presentation (pdf, 16 slides) and its source (org).
Have fun with wisp syntax!
Update (2016-07-12): wisp v0.9.1 released with a fix for multiline strings and many additional examples. For more info, see the NEWS file. To test it, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.1.tar.gz; tar xf wisp-0.9.1.tar.gz ; cd wisp-0.9.1/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2016-01-30): I presented Wisp in the Guile devroom at FOSDEM. The reception was unexpectedly positive — given some of the backlash the readable project got I expected an exceptionally sceptical audience, but people rather asked about ways to put Wisp to good use, for example in templates, whether it works in the REPL (yes, it does) and whether it could help people start into Scheme. The atmosphere in the Guile devroom was very constructive and friendly during all talks, and I’m happy I could meet the Hackers there in person. I’m definitely taking good memories with me. Sadly the video did not make it, but the schedule-page includes the presentation (pdf, 10 slides) and its source (org).
Have fun with wisp syntax!
Update (2016-01-04): Wisp is available in GNU Guix! Thanks to the package from Christopher Webber you can try Wisp easily on top of any distribution:
`guix package -i guile guile-wispguile --language=wisp`
This already gives you Wisp at the REPL (take care to follow all instructions for installing Guix on top of another distro, especially the locales).
Have fun with wisp syntax!
Update (2015-10-01): wisp v0.9.0 released which no longer depends on Python for bootstrapping releases (but ./configure still asks for it — a fix for another day). And thanks to Christopher Webber there is now a patch to install wisp within GNU Guix. For more info, see the NEWS file. To test it, install Guile 2.0.11 or later and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.9.0.tar.gz; tar xf wisp-0.9.0.tar.gz ; cd wisp-0.9.0/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2015-09-12): wisp v0.8.6 released with fixed macros in interpreted code, chunking by top-level forms, `: .` parsed as nothing, ending chunks with a trailing period, updated example evolve and added examples newbase60, cli, cholesky decomposition, closure and hoist in loop. For more info, see the NEWS file.To test it, install Guile 2.0.x or 2.2.x and Python 3 and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.8.6.tar.gz; tar xf wisp-0.8.6.tar.gz ; cd wisp-0.8.6/; ./configure; make check; examples/newbase60.w 123`
If it prints 23 (123 in NewBase60), your wisp is fully operational.
That’s it - have fun with wisp syntax! And a happy time together for the ones who merge their paths today ☺
Update (2015-04-10): wisp v0.8.3 released with line information in backtraces. For more info, see the NEWS file.To test it, install Guile 2.0.x or 2.2.x and Python 3 and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.8.3.tar.gz; tar xf wisp-0.8.3.tar.gz ; cd wisp-0.8.3/; ./configure; make check; guile -L . --language=wisp tests/factorial.w; echo`
If it prints 120120 (two times 120, the factorial of 5), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2015-03-18): wisp v0.8.2 released with reader bugfixes, new examples and an updated draft for SRFI 119 (wisp). For more info, see the NEWS file.To test it, install Guile 2.0.x or 2.2.x and Python 3 and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.8.2.tar.gz; tar xf wisp-0.8.2.tar.gz ; cd wisp-0.8.2/; ./configure; make check; guile -L . --language=wisp tests/factorial.w; echo`
If it prints 120120 (two times 120, the factorial of 5), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2015-02-03): The wisp SRFI just got into draft state: SRFI-119 — on its way to an official Scheme Request For Implementation!
Update (2014-11-19): wisp v0.8.1 released with reader bugfixes. To test it, install Guile 2.0.x and Python 3 and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.8.1.tar.gz; tar xf wisp-0.8.1.tar.gz ; cd wisp-0.8.1/; ./configure; make check; guile -L . --language=wisp tests/factorial.w; echo`
If it prints 120120 (two times 120, the factorial of 5), your wisp is fully operational.
That’s it - have fun with wisp syntax!
Update (2014-11-06): wisp v0.8.0 released! The new parser now passes the testsuite and wisp files can be executed directly. For more details, see the NEWS file. To test it, install Guile 2.0.x and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.8.0.tar.gz; tar xf wisp-0.8.0.tar.gz ; cd wisp-0.8.0/; ./configure; make check; guile -L . --language=wisp tests/factorial.w; echo`
If it prints 120120 (two times 120, the factorial of 5), your wisp is fully operational.
That’s it - have fun with wisp syntax!
On a personal note: It’s mindboggling that I could get this far! This is actually a fully bootstrapped indentation sensitive programming language with all the power of Scheme underneath, and it’s a one-person when-my-wife-and-children-sleep sideproject. The extensibility of Guile is awesome!
Update (2014-10-17): wisp v0.6.6 has a new implementation of the parser which now uses the scheme read function. `wisp-scheme.w` parses directly to a scheme syntax-tree instead of a scheme file to be more suitable to an SRFI. For more details, see the NEWS file. To test it, install Guile 2.0.x and bootstrap wisp:
`wget https://bitbucket.org/ArneBab/wisp/downloads/wisp-0.6.6.tar.gz; tar xf wisp-0.6.6.tar.gz; cd wisp-0.6.6; ./configure; make; guile -L . --language=wisp`
That’s it - have fun with wisp syntax at the REPL!
Caveat: It does not support the ' prefix yet (syntax point 4).
Update (2014-01-04): Resolved the name-clash together with Steve Purcell und Kris Jenkins: the javascript wisp-mode was renamed to wispjs-mode and wisp.el is called wisp-mode 0.1.5 again. It provides syntax highlighting for Emacs and minimal indentation support via tab. You can install it with `M-x package-install wisp-mode`
Update (2014-01-03): wisp-mode.el was renamed to wisp 0.1.4 to avoid a name clash with wisp-mode for the javascript-based wisp.
Update (2013-09-13): Wisp now has a REPL! Thanks go to GNU Guile and especially Mark Weaver, who guided me through the process (along with nalaginrut who answered my first clueless questions…).
To test the REPL, get the current code snapshot, unpack it, run `./bootstrap.sh`, start guile with `\$ guile -L .` (requires guile 2.x) and enter `,language wisp`.
Example usage:
`display "Hello World!\n"`
then hit enter thrice.
Voilà, you have wisp at the REPL!
Caveeat: the wisp-parser is still experimental and contains known bugs. Use it for testing, but please do not rely on it for important stuff, yet.
Update (2013-09-10): wisp-guile.w can now parse itself! Bootstrapping: The magical feeling of seeing a language (dialect) grow up to live by itself: `python3 wisp.py wisp-guile.w > 1 && guile 1 wisp-guile.w > 2 && guile 2 wisp-guile.w > 3 && diff 2 3`. Starting today, wisp is implemented in wisp.
Update (2013-08-08): Wisp 0.3.1 released (Changelog).
Willkommen im Weltenwald!
((λ()'Dr.ArneBab))