Warning: This is the manual of the legacy Guile 2.2 series. You may want to read the manual of the current stable series instead.

6.6.5.2 String Predicates

The following procedures can be used to check whether a given string fulfills some specified property.

Scheme Procedure: string? obj

C Function: scm_string_p (obj)

Return #t if obj is a string, else #f.

C Function: int scm_is_string (SCM obj)

Returns 1 if obj is a string, 0 otherwise.

Scheme Procedure: string-null? str

C Function: scm_string_null_p (str)

Return #t if str’s length is zero, and #f otherwise.

(string-null? "")  ⇒ #t
y                    ⇒ "foo"
(string-null? y)     ⇒ #f

Scheme Procedure: string-any char_pred s [start [end]]

C Function: scm_string_any (char_pred, s, start, end)

Check if char_pred is true for any character in string s.

char_pred can be a character to check for any equal to that, or a character set (see Character Sets) to check for any in that set, or a predicate procedure to call.

For a procedure, calls (char_pred c) are made successively on the characters from start to end. If char_pred returns true (ie. non-#f), string-any stops and that return value is the return from string-any. The call on the last character (ie. at end-1), if that point is reached, is a tail call.

If there are no characters in s (ie. start equals end) then the return is #f.

Scheme Procedure: string-every char_pred s [start [end]]

C Function: scm_string_every (char_pred, s, start, end)

Check if char_pred is true for every character in string s.

char_pred can be a character to check for every character equal to that, or a character set (see Character Sets) to check for every character being in that set, or a predicate procedure to call.

For a procedure, calls (char_pred c) are made successively on the characters from start to end. If char_pred returns #f, string-every stops and returns #f. The call on the last character (ie. at end-1), if that point is reached, is a tail call and the return from that call is the return from string-every.

If there are no characters in s (ie. start equals end) then the return is #t.