chickadee » srfi-13 » string-index

string-index (string-index-right) searches through the string from the left (right), returning the index of the first occurrence of a character which

• equals CHAR/CHAR-SET/PRED (if it is a character);
• is in CHAR/CHAR-SET/PRED (if it is a character set);
• satisfies the predicate CHAR/CHAR-SET/PRED (if it is a procedure).

If no match is found, the functions return false.

The START and END parameters specify the beginning and end indices of the search; the search includes the start index, but not the end index. Be careful of "fencepost" considerations: when searching right-to-left, the first index considered is

END-1

whereas when searching left-to-right, the first index considered is

START

That is, the start/end indices describe a same half-open interval [START,END) in these procedures that they do in all the other SRFI 13 procedures.

The skip functions are similar, but use the complement of the criteria: they search for the first char that doesn't satisfy the test. E.g., to skip over initial whitespace, say

(cond ((string-skip s char-set:whitespace) =>

       (lambda (i) ...)) ; s[i] is not whitespace.
      ...)