Chapter 29

string.ss: String Utilities

(eval-string str [err-display err-result])      PROCEDURE

Reads and evaluates S-expressions from the string str, returning a result for each expression. Note that if str contains only whitespace and comments, zero values are returned, while if str contains two expressions, two values are returned.

If err-display is not #f (the default), then errors are caught and err-display is used as the error display handler. If err-result is specified, it must be a thunk that returns a value to be returned when an error is caught; otherwise, #f is returned when an error is caught.

(expr->string expr)      PROCEDURE

Prints expr into a string and returns the string.

(read-from-string str [err-display err-result])      PROCEDURE

Reads the first S-expression from the string str and returns it. The err-display and err-result are as in eval-str.

(read-from-string-all str [err-display err-result])      PROCEDURE

Reads all S-expressions from the string str and returns them in a list. The err-display and err-result are as in eval-str.

(regexp-match* pattern str [start-k end-k])      PROCEDURE

Like regexp-match (see section 10 in PLT MzScheme: Language Manual), but the result is a list of strings corresponding to a sequence of matches of pattern in str. (Unlike regexp-match, results for parenthesized sub-patterns in pattern are not returned.) If pattern matches a zero-length string along the way, the exn:user exception is raised.

If str contains no matches (in the range start to end), null is returned. Otherwise, each string in the resulting list is a distinct substring of str that matches pattern.

(regexp-match-exact? pattern str)      PROCEDURE

This procedure is like MzScheme's built-in regexp-match (see section 10 in PLT MzScheme: Language Manual), but the result is always #t or #f; #t is only returned when the entire string str matches pattern.

(regexp-match-positions* pattern str [start-k end-k])      PROCEDURE

Like regexp-match-positions (see section 10 in PLT MzScheme: Language Manual), but the result is a list of integer pairs corresponding to a sequence of matches of pattern in str. (Unlike regexp-match-positions, results for parenthesized sub-patterns in pattern are not returned.) If pattern matches a zero-length string along the way, the exn:user exception is raised.

If str contains no matches, null is returned.

(regexp-quote str [case-sensitive?])      PROCEDURE

Produces a string suitable for use with regexp (see section 10 in PLT MzScheme: Language Manual) to match the literal sequence of characters in str. If case-sensitive? is true, the resulting regexp matches letters in str case-insensitively, otherwise (and by default) it matches case-sensitively.

(regexp-replace-quote str)      PROCEDURE

Produces a string suitable for use as the third argument to regexp-replace (see section 10 in PLT MzScheme: Language Manual), to insert the literal sequence of characters in str as a replacement. Concretely, every backslash in str is protected by a quoting backslash.

(regexp-split pattern str [start-k end-k])      PROCEDURE

The complement of regexp-match* (see above): the result is a list of sub-strings in str that are separated by matches to pattern; adjacent matches are separated with "". If pattern matches a zero-length string along the way, the exn:user exception is raised.

If str contains no matches (in the range start to end), the result will be a list containing str (from start to end). If a match occurs at the beginning of str (at start), the resulting list will start with an empty string, and if a match occurs at the end (at end), the list will end with an empty string.

(string-lowercase! str)      PROCEDURE

Destructively changes str to contain only lowercase characters.

(string-uppercase! str)      PROCEDURE

Destructively changes str to contain only uppercase characters.