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diff --git a/posts/2018-09-01-guile-picture-language.md b/posts/2018-09-01-guile-picture-language.md new file mode 100644 index 0000000..3fcac51 --- /dev/null +++ b/posts/2018-09-01-guile-picture-language.md @@ -0,0 +1,74 @@ +title: A simple picture language for GNU Guile +date: 2018-09-01 23:00 +tags: planet-fsfe-en, free software, guile +--- + +One thing that I really love about Racket is its [picture +language](https://docs.racket-lang.org/pict/), which allows you to +play with geometric shapes in an interactive session in Dr Racket. +The shapes are displayed right there in the REPL, just like numbers or +strings. Instead of writing a programme that prints "hello world" or +that computes the Fibonacci numbers, one could write a programme that +composes differently rotated, coloured shapes and prints those +instead. + +I use [GNU Guile](https://gnu.org/software/guile) for my own projects, +and sadly we don't have an equivalent of Racket's picture language or +the Dr Racket editor environment. So I made something: a [simple +picture language for GNU +Guile](https://git.elephly.net/software/guile-picture-language.git). +It provides simple primitive procedures to generate shapes, to +manipulate them, and to compose them. + +Download the single Guile module containing the implementation: + + mkdir ~/pict + wget https://elephly.net/downies/pict.scm + +To actually see these shapes as you play with them, you need to use a +graphical instance of [GNU Emacs](https://gnu.org/software/emacs) with +[Geiser](http://www.nongnu.org/geiser/). + +Start geiser in Emacs and load the module: + + M-x run-guile + (add-to-load-path (string-append (getenv "HOME") "/pict")) + ,use (pict) + +Let’s play! + + (circle 100) + +If you see a pretty circle: hooray! Let’s play some more: + + (colorize (circle 100) "red") + (disk 80) + (rectangle 50 100) + +Let's compose and manipulate some shapes! + + ,use (srfi srfi-1) + ,use (srfi srfi-26) + (apply hc-append + (map (cut circle <>) + (iota 10 2 4))) + + (apply cc-superimpose + (map (cut circle <>) + (iota 10 2 4))) + + (apply hc-append + (map (cut rotate (rectangle 10 30) <>) + (iota 36 0 10))) + + (apply cc-superimpose + (map (cut rotate (triangle 100 300) <>) + (iota 36 0 10))) + +There are many more procedures for primitive shapes and for +manipulations. Almost all procedures in pict.scm have docstrings, so +feel free to explore the code to find fun things to play with! + +PS: I realize that it's silly to have a blog post about a picture +language without any pictures. Instead of thinking about this now, +get the module and make some pretty pictures yourself! |