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instrx ( haystack_string_expression , regular_expression )
instrx ( haystack_string_expression , regular_expression , start_expression )

returns integer_expression

Check to see if the text represented by the regular expression regular_expression is contained in the string haystack_string_expression. If it is, then this function will return the index of starting character of the first place where needle_string_expression occurs. Otherwise, this function will return 0.

You may optionally specify a starting location for the search to begin start_expression. If the start is 1 or greater the search will begin from the specified character from the start. If the start is < 0 then the search will begin from the nth character from the end. The search will ALWAYS look forward.

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.