indexfind pattern in string function

Syntax   index (s , patt : string ) : int

Description   The index function is used to find the position of patt within string s. For example, index ( "chair", "air" ) is 3.

Example   This program outputs 2, because "ill" is a substring of "willing", starting at the second character of "willing".

        var word : string := "willing"
        put index ( word, "ill" )
Details   If the pattern (patt) does not appear in the string (s), index returns 0 (zero). For example, here is an if statement that checks to see if string s contains a blank:

        if index ( s, " " ) not= 0 then 
The index is sometimes used to efficiently determine if a character is one of a given set of characters. For example, here is an if statement that checks to see if ch, which is declared using var ch : string (1), is a digit:

        if index ( "0123456789", ch) not= 0 then 
If a string contains more that one occurrence of the pattern, the leftmost location is returned. For example, index ("pingpong", "ng") returns 3.

If patt is the null string, the result is 1.