INSTR

Search for an occurrence of a substring within a string. * Syntax ```sbsyntax INSTR { startIndex% }, string$, substring$ OUT index% ``` |* Input | Description | | `startIndex%` | The index within `string$` to start searching from. Optional, default 0. | | `string$` | The string to search within. | | `substring$` | The substring to search for. | |* Output | Description | | `index%` | The index of the substring found within `string$`. -1 if no occurrence is found | `INSTR` will return only the index of the first occurrence of `substring$` it finds, starting from the `startIndex%`. If `starIndex%` is omitted, then the search starts from the beginning of `string$` (index 0). If `substring$` is not found, then `index%` will be -1. * Examples ```sb4 'find the letter 'a' within this string. PRINT INSTR("The quick brown fox jumps over the lazy dog.","a") '36 ``` ```sb4 'find the first "chuck" starting at character 40 CONST #CHUCK="How much wood could a woodchuck chuck if a woodchuck could chuck wood?" INSTR 40,#CHUCK,"chuck" OUT I% PRINT I% '47 ``` ```sb4 'this match will fail PRINT INSTR("######","!") '-1 ``` * Notes ** Empty Substring If `substring$` is empty, /every/ index in any `string$` will match it. ```sb4 'these all match PRINT INSTR("Hello, world!","") '0 PRINT INSTR(3,"Hello, world!","") '3 PRINT INSTR(7,"Hello, world!","") '7 ``` An interesting quirk of this is that the empty string will match at one index past the end of the string. ```sb4 '3 is one past the end of the string PRINT INSTR(3,"ABC","") '3 PRINT INSTR(4,"ABC","") '-1 ```