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  ANSI Common Lisp   23 Reader   23.2 Dictionary of Reader

23.2.11 set-syntax-from-char Function

Syntax:
set-syntax-from-char to-char from-char &optional to-readtable from-readtable    t

Arguments and Values:
to-char - a character.

from-char - a character.

to-readtable - a readtable. The default is the current readtable.

from-readtable - a readtable designator. The default is the standard readtable.

Description:
set-syntax-from-char makes the syntax of to-char in to-readtable be the same as the syntax of from-char in from-readtable.

set-syntax-from-char copies the syntax types of from-char. If from-char is a macro character, its reader macro function is copied also. If the character is a dispatching macro character, its entire dispatch table of reader macro functions is copied. The constituent traits of from-char are not copied.

A macro definition from a character such as " can be copied to another character; the standard definition for " looks for another character that is the same as the character that invoked it. The definition of ( can not be meaningfully copied to {, on the other hand. The result is that lists are of the form {a b c), not {a b c}, because the definition always looks for a closing parenthesis, not a closing brace.

Examples:
 (set-syntax-from-char #\7 #\;)   T
 123579  1235

Side Effects:
The to-readtable is modified.

Affected By:
The existing values in the from-readtable.

See Also:
set-macro-character, make-dispatch-macro-character, Section 2.1.4 Character Syntax Types

Notes:
The constituent traits of a character are "hard wired" into the parser for extended tokens. For example, if the definition of S is copied to *, then * will become a constituent that is alphabetic2 but that cannot be used as a short float exponent marker. For further information, see Section 2.1.4.2 Constituent Traits.

Allegro CL Implementation Details:
None.

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