Gauche — Practical Scheme Scripting
A fast, practical R7RS Scheme implementation for scripting and
real-world programming.
Download Gauche
Latest release: 0.9.15
Documentation
Latest news
2025/12/14
Gauche-gtk2 0.6.2
Minor update. A new API addition and adaptation to newer Gauche.
Past announcements ...
Why Gauche?
Designed for scripting
Gauche emphasizes quick startup time, smooth integration with the
operating system, and expressive syntax, making it suitable for
automation, build tools, and shell-like scripting.
Batteries included
Gauche comes with networking, Unicode strings
and regular expressions, threads,
various algorithm and data structures,
and more—available out of the box.
Modern Scheme and beyond
Gauche is compatible with R7RS (small and large) and supports a large
collection of finalized SRFIs, along with language
extensions, including integrated lazy sequences,
object system with metaobject protocol, and more.
Stable and maintained
Developed and used for over two decades, Gauche focuses on stability,
backward compatibility, and long-term maintainability.
A Taste of Gauche
;; Generator of Fibonacci numbers. ^ is a shorthand of lambda.
(define (make-fib-gen)
(let ([a 1] [b 1])
(^[] (let1 c (+ a b) (rotate! a b c)))))
;; Create a lazy infinite list of Fibonacci numbers
(define *fibs* (generator->lseq (make-fib-gen)))
;; Take first 20 Fibonacci numbers
(take *fibs* 20)
;⇒ (1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765)
;; What is the 100th Fibonacci number?
(~ *fibs* 100)
;⇒ 573147844013817084101
;; Find n such that Fib(n) exceeds 2^64 for the first time
(use scheme.list)
(length (take-while (cut > (expt 2 64) <>) *fibs*))
;⇒ 93
;; Draw a Fibonacci spiral
(use gauche.lazy)
(define (fib-spiral xsize ysize)
;; List of points of the start of the quarter arc. We use complex numbers, so
;; rotation is just multiplication.
(define *Pn*
(lmap-accum (^[Fn rot acc]
(let1 next (+ acc (* rot (make-rectangular Fn Fn)))
(values acc next)))
0 *fibs* (circular-list 1 -i -1 +i)))
(define (draw-arc Fn Pn Pn+1)
(format #t "
(real-part Pn) (imag-part Pn) Fn Fn (real-part Pn+1) (imag-part Pn+1)))
;; Emit SVG content
(print #""))
;; Save the generated SVG to a file.
(with-output-to-file "fib-spiral.svg" (cut fib-spiral 600 480))
Here's the generated svg file:
Extensions
Gauche has a growing ecosystem of libraries and extensions, including
community-maintained
SRFIs
and practical tools.
Over 200 libraries and extensions
Package management via
gauche-package
command
Easy to write and distribute your own extensions
Browse available extensions