You are looking at historical revision 1302 of this page. It may differ significantly from its current revision.
Non standard read syntax
#| ... |#
A multiline block comment. May be nested. Implements SRFI-30
#;EXPRESSION
Treats EXPRESSION as a comment.
#,(CONSTRUCTORNAME DATUM ...)
Allows user-defined extension of external representations. (For more information see the documentation for SRFI-10)
#'EXPRESSION
An abbreviation for (syntax EXPRESSION).
#$EXPRESSION
An abbreviation for (location EXPRESSION).
#:SYMBOL
Syntax for keywords. Keywords are symbols that evaluate to themselves, and as such don't have to be quoted.
#<<TAG
Specifies a multiline string constant. Anything up to a line equal to TAG (or end of file) will be returned as a single string:
(define msg #<<END "Hello, world!", she said. END )
is equivalent to
(define msg "\"Hello, world!\", she said.") #<#TAG
Similar to #<<, but allows substitution of embedded Scheme expressions prefixed with # and optionally enclosed in curly brackets. Two consecutive #s are translated to a single #:
(define three 3)
(display #<#EOF
This is a simple string with an embedded `##' character
and substituted expressions: (+ three 99) ==> #(+ three 99)
(three is "#{three}")
EOF
)
prints
This is a simple string with an embedded `#' character and substituted expressions: (+ three 99) ==> 102 (three is "3") #> ... <#
Abbreviation for foreign-declare " ... ").
#>? ... <#
Abbreviation for (foreign-parse " ... ").
#>! ... <#
Abbreviation for (foreign-parse(declare " ... ").
#%...
Reads like a normal symbol.
#!...
Treated as a commment and ignores everything up the end of the current line. The keywords #!optional, #!rest and #!key are handled separately and returned as normal symbols. The special (self-evaluating) symbol #!eof is read as the end-of-file object. Note that if this constant appears at top-level in a loaded file, it is indistiguishable from normal end-of-file.
#cs...
Read the next expression in case-sensitive mode (regardless of the current global setting).
#ci...
Read the next expression in case-insensitive mode (regardless of the current global setting).
#+FEATURE EXPR
Equivalent to
(cond-expand (FEATURE EXPR) (else))
Previous: Extensions to the standard