set-syntax-from-char to-char from-char &optional to-readtable from-readtable → t

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.

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.

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

The to-readtable is modified.

The existing values in the from-readtable.

set-macro-character, make-dispatch-macro-character, Section 2.1.4 (Character Syntax Types)

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).