The BBC and Master Computer Public Domain Library

9E58 '+' operator - addition

Submitted by Steve Fewell

Description:

Check the value type (in A).
If variable type = 0 then goto the String Addition routine.

If variable type is negative then the first value is a Float, so jump to &9E94, which
does the following:
* Push FWA to Stack
* Get the second value from the expression handler (level 5)
* If second value is a String then generate a Type Mismatch error.
* If second value is an Integer then convert it to a Float
* Pop the first Float value from Stack to argp (&4A, &4B)
* Call the Floating-Point Addition routine to add the values (&A68D)
* Jump to 9E4F (Expression handler level 4) to check for further + or - operators.

Otherwise, the value is Integer, so push the first value to the stack and call the
Expression Handler level 5 routine (&9FC4) to get the second value to add.
If the second value is a string then generate a Type Mismatch error.

If the second value is a Float then jump to &9EB0 to do the following:
* Pop the first value (the Integer) from the Stack
* Push the second value (the Float) to the Stack
* Convert the Integer to a Float (and put it in the FWA).
* Pop the second Float value from Stack to argp (&4A, &4B)
* Call the Floating-Point Addition routine to add the values (&A68D)
* Jump to 9E4F (Expression handler level 4) to check for further + or - operators.

Otherwise, both values are Integers, so carry out the Integer Addition routine. This
routine automatically jumps back to 9E4F on completion, to check for further + or - operators.

Disassembly for the '+' Operator - Addition routine

Disassembly for the Floating Point '+' Operator