ReturnValue

Description

ReturnValue is a semi-obsolete method that was used before TRSE supported functions. Calling "ReturnValue( int / byte )" will load the parameter value into the internal byte / int registers for the current CPU, and return from the function (rts/ret etc), allowing for function-like return values as such: procedure Calculate( i : byte ); begin // will return a byte value i + 2 // on the 6502/z80, the value will be stored in a, on the x86 in al etc ReturnValue( i + 2 ); end; ... myByte := Calculate( j ); Note: A major flaw with "Returnvalue" - and why functions should be used instead - is that the compiler is unable to obtain the correct return value type. The following code will therefore fail: // The compiler doesnt know whether "Calculate" returns a byte or an integer, but since // "someInteger" is an int it assumes this incorrectly. // Buggy on the 6502 (since the contents of "y" is unknown) // Fatal on the Z80 since bytes are stored in "a" while ints in "hl" someInteger := Calculate( j ); Internally, a function in TRSE is just a procedure with a defined return value type that automatically calls "Returnvalue" on exit, but the compiler now has the possibility of casting the returned value to the correct write type. The correct way of defining the function would be function Calculate( i : byte ) : byte; begin Calculate := i + 2; end; // or function Calculate( i : byte ) : byte; begin ReturnValue( i + 2 ); end;