Function

Summary

Count the occurrences of a pattern in a string.

Package

lispworks

Signature

count-regexp-occurrences pattern string &key start end overlap case-sensitive => count

Arguments

pattern

A string or precompiled regular expression object.

string

A string.

start, end

Bounding index designators of string.

overlap

A generalized boolean.

case-sensitive

A generalized boolean.

Values

count

An integer.

Description

The function count-regexp-occurrences counts the occurrences of pattern in the part of string bounded by start and end.

If pattern is a string, count-regexp-occurrences precompiles it first. If you use count-regexp-occurrences with the same pattern string several times, it is better to precompile it using precompile-regexp.

start and end have the sames meaning as in count and other Common Lisp sequence functions.

case-sensitive controls whether a string pattern is precompiled as a case sensitive or case insensitive search. A non-nil value means a case sensitive search. The value nil (the default) means a case insensitive search.

If overlap is false (the default), then count-regexp-occurrences counts matches that to not overlap. If overlap is non-nil, matches can overlap, and count-regexp-occurrences finds all of the ways in which the pattern can be matched inside string.

The regular expression syntax used by count-regexp-occurrences is similar to that used by Emacs, as described in the "Regular expression syntax" section of the LispWorks Editor User Guide . If you use Help > Search to locate this section in the LispWorks IDE, then select the Contents radio button.

Examples

(count-regexp-occurrences "aaa" "aaaaa")

=> 

1

(count-regexp-occurrences "aaa" "aaaaa" :overlap t)  

=>

3

(count-regexp-occurrences "12" "81267124")  

=>

2

(count-regexp-occurrences "12" "81267124" :start 4) 

=>

1

(let* ((path (example-file

              "capi/elements/text-input-pane.lisp"))

       (file-string (file-string path)))

  (count-regexp-occurrences ":title" file-string))

=> 

20   ; in LispWorks 7.1

See also

find-regexp-in-string
precompile-regexp