For Gauche 0.9.5

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1.1 Overview of Gauche

Gauche is a Scheme script engine; it reads Scheme programs, compiles it on-the-fly and executes it on a virtual machine. Gauche conforms the language standard "Revised^7 Report on the Algorithmic Language Scheme" (R7RS), and supports various common libraries defined in SRFIs (

The goal of Gauche is to provide a handy tool for programmers and system administrators to handle daily works conveniently and efficiently in the production environment.

There are lots of Scheme implementations available, and each of them has its design emphasis and weaknesses. Gauche is designed with emphasis on the following criteria.

Quick startup

One of the situation Gauche is aiming at is in the production environment, where you write ten-lines throw-away script that may invoked very frequently. This includes CGI scripts as well. Gauche provides frequently used common features as a part of rich built-in functions or precompiled Scheme libraries that can be loaded very quickly.

Fully utilizing multi-core

Gauche supports native threads on most platforms. The internals are fully aware of preemptive/concurrent threads (that is, no “giant global lock”), so that you can utilize multiple cores on your machine.

Multibyte strings

We can no longer live happily in ASCII-only or 1-byte-per-character world. The practical language implementations are required to handle multibyte (wide) characters. Gauche supports multibyte strings natively, providing robust and consistent support than ad hoc library-level implementation. See Multibyte strings, for details.

Integrated object system

A powerful CLOS-like object system with MetaObject protocol (mostly compatible with STklos and Guile) is provided.

System interface

Although Scheme abstracts lots of details of the machine, sometimes you have to bypass these high-level layers and go down to the basement to make things work. Gauche has built-in support of most of POSIX.1 system calls. Other modules, such as networking module, usually provide both high-level abstract interface and low-level interface close to system calls.

Enhanced I/O

No real application can be written without dealing with I/O. Scheme neatly abstracts I/O as a port, but defines least operations on it. Gauche uses a port object as a unified abstraction, providing utility functions to operate on the underlying I/O system. See Input and output, for the basic I/O support.

Extended language

Gauche is not just an implementation of Scheme; it has some language-level enhancements. For example, lazy sequences allows you to have lazy data structures that behaves as if they’re ordinary lists (except that they’re realized lazily). It is different from library-level lazy structure implementation such as streams (srfi-41), in a sense that you can use any list-processing procedures on lazy sequences. It enables programs to use lazy algorithms more liberally.

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