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instrx ( haystack_expr , regex_expr )
instrx ( haystack_expr , regex_expr , start_expr )

returns positive_integer_expr

Check to see if the text represented by the regular expression regex_expr is contained in the string haystack_expr. If it is, then this function will return the index of starting character of the first place where needle_expr occurs. Otherwise, this function will return 0. You may also specify an optional starting location for the search to begin start_expr. Unlike INSTR, INSTRX allows ignoring specific variations (case sentive, spelling etc).

String indices begin at 1.

print instrx("HeLLo", "[Ll]o")
print instrx("Hello, Kitti","[Ii]",10)

will display

4
12

instrx can be used to test if a string matches a regular expression. In for following example the function isnumber returns true if the string passed is in for format of a floating point number and false if not.

function isnumber(s$)
   # return true if a number - false of not
   return instrx(s$,"^-?\d+\.?\d*$") <> 0
end function

By default the nature of regular expressions is “greedy”. This behaviour can be changed using the RegexMinimal statement.