The BBC and Master Computer Public Domain Library

AB8A INT

Submitted by Steve Fewell

Description:

Call routine &AD36 to get the Value at the BASIC Text pointer B location.
If the result is a String value then issue a Type mismatch error.
If the result is an Integer value (A = #&40) then exit as the value is already an Integer.

Push the FWA sign byte (6502 processor flags when &2E byte loaded) to the 6502 stack.
Call routine &8275 to move the fractional part of the FWA value out of the FWA and into the FWB mantissa and to convert
the FWA value to a two's complement format number (if the FWA sign bit is negative).

Retrieve the FWA sign byte status from the 6502 stack.
If the FWA was positive then copy the FWA mantissa to the IWA and exit with A = #&40 (as the result is an Integer);
now the IWA contaions the Integer FWA value.

If the FWA was negative then convert the value to Integer as follows:
* If the FWB Mantissa (bytes &3D to &40) is zero then there is no fractional part, so copy the FWA mantissa to
the IWA and exit with A = #&40 (as the result is an Integer).
* Call &82C8 to perform a reverse order complement of the FWA value (to make the value a positive Integer value).
* Call &830D to add 1 to the FWA Mantissa value.
* Call &82C8 to perform a reverse order complement of the FWA value to reverse the previous complement resulting in the
two's complement value.
* Copy the FWA Mantissa to the IWA and exit with A = #&40 (as the result is an Integer).

Disassembly for the INT routine

Disassembly for the Add 1.0 to the FWA Mantissa value routine