3.1.4 Error Messages There are several errors that might occur in the built-in functions. Just one error message is only relevant for all the built-in functions, that is number 40 (Incorrect call to routine). In fact, an implementation of REXX can choose to use that for any problem it encounters in the built-in functions. Depending on the implementation, other error messages might be used as well. Error message number 26 (Invalid whole number) might be used for any case where a parameter should have been a whole number, or where a whole number is out of range. It is implied that this error message can be used in these situations, and it is not explicitly mentioned in the description of the functions. Other general error messages that might be used in the built-in functions are error number 41 (Bad arithmetic conversion) for any parameter that should have been a valid REXX number. The error message 15 (Invalid binary or hexadecimal string) might occur in any of the conversion routines that converts from binary or hexadecimal format (B2X(), X2B(), X2C(), X2D()). And of course the more general error messages like error message 5 (Machine resources exhausted) can occur. Generally, it is taken as granted that these error messages might occur for any relevant built-in function, and this will not be restated for each function. When other error messages than these are relevant, it will be mentioned in the text. In REXX, it is in general not an error to specify a start position that is larger than the length of the string, or a length that refers to parts of a string that is beyond the end of that string. The meaning of such instances will depend on the context, and are described for each function.