4.1 Lexical structure

Gauche extends R5RS Scheme parser in some ways:

Nested block comments (SRFI-30)

A text surrounded by '#|' and '|#' becomes a comment. It can be nested.

Numeric literals

Either integral part or fraction part of inexact real numbers can be omitted if it is zero, i.e. 30., .25, -.4 are read as real numbers. Using '#' as insignificant digits is not supported.

Symbol names

Symbol names are case sensitive by default (See section 2.3 Case-sensitivity). Symbol name can begin with digits, '+' or '-', as long as the entire token doesn't consist valid number syntax. Other weird characters can be included in a symbol name by surrounding it with '|', e.g. '|this is a symbol|'. See section 6.5 Symbols, for details.

Character literal by character code

Character literals can be written using its code, by #\xNN (Gauche internal code) or #\uNN (Unicode). See section 6.8 Characters, for details.

Extended sharp syntax

Many more special tokens begins with '#' is defined. See the table below.

The table below lists sharp-syntaxes.

#!	[SRFI-22] Specifies interpreter at the beginning of file. Scheme loader ignores the line.
#", ##, #$, #%, #&, #'	Unused.
#(	[R5RS] Introduces a vector.
#)	Unused.
#*	If followed by a double quote, denotes an incomplete string. See section 6.10 Strings.
#+	Unused.
#,	[SRFI-10] Introduces reader constructor syntax.
#-, #.	Unused.
#/	Introduces a literal regular expression. See section 6.11 Regular expression.
#0 ... #9	Reserved for shared structure reference.
#:, #;	Unused
#<	Introduces an unreadable object.
#=, #>	Unused.
#?	Introduces debug macros. See section 3.3 Debugging.
#@	Unused.
#a	Unused.
#b	[R5RS] Binary number prefix.
#c	Unused.
#d	[R5RS] Decimal number prefix.
#e	[R5RS] Exact number prefix.
#f	[R5RS] Boolean false, or introducing SRFI-4 uniform vector. See section 9.24 gauche.uvector - Uniform vectors.
#g, #h	Unused.
#i	[R5RS] Inxact number prefix.
#j, #k, #l, #m, #n	Unused.
#o	[R5RS] Octal number prefix.
#p, #q, #r	Unused.
#s	[SRFI-4] introducing SRFI-4 uniform vector. See section 9.24 gauche.uvector - Uniform vectors.
#t	[R5RS] Boolean true.
#u	[SRFI-4] introducing SRFI-4 uniform vector. See section 9.24 gauche.uvector - Uniform vectors.
#v, #w	Unused.
#x	[R5RS] Hexadecimal number prefix.
#y, #z	Unused.
#[	Introduces a literal character set. See section 6.9 Character Set.
#\	[R5RS] Introduces a literal character. See section 6.8 Characters.
#], #^, #_	Unused.
#`	Introduces an interpolated string. See section 6.10.4 String interpolation.
#{	Unused.
#|	[SRFI-30] Introduces a block comment. Comment ends by matching '|#'.
#}, #~	Unused.