Arithmetic Function (arithmetic_function) 
An arithmetic function (arithmetic_function) is a function that produces a numerical value.
Structure
Syntax
<arithmetic_function> ::= ABS(<expression>) | CEIL(<expression>) | EXP(<expression>) | FIXED(<expression>[,<unsigned_integer>[,<unsigned_integer>]]) | FLOAT(<expression>[,<unsigned_integer>]) | FLOOR(<expression>) | INDEX(<string_spec>,<string_spec>[,<expression>[,<expression>]]) | LENGTH(<expression>) | LN(<expression>) | LOG(<expression>,<expression)> | NOROUND(<expression>) | PI | POWER(<expression>,<expression>) | ROUND(<expression>[,<expression>]) | SIGN(<expression>) | SQRT(<expression>) | TRUNC(<expression>[,<expression>]) <string_spec> ::= <expression>
End of the code.
Explanation
Only expressions that produce an alphanumeric value are permitted as string specification string_spec in the INDEX function.