#if

Syntax:

    #if Condition
      ...
    [#else]
      ...
    #endif

Explanation:

The #if directive is used to prevent a section of code from compiling unless Condition is true.

Condition has the same syntax as the condition in a normal GCBASIC If command. The only difference is that it uses constants instead of variables, and does not use "then".

Example:

    'This program will pulse an adjustable number of pins on PORTB
    'The number of pins is controlled by the FlashPins constant
    #chip 16F88, 8

    'The number of pins to flash
    #define FlashPins 2

    'Initialise
    Dir PORTB Out

    'Main loop
    Do
        #if FlashPins >= 1
            PulseOut PORTB.0, 250 ms          ' <<< compiled in only when FlashPins is 1 or more
        #endif
        #if FlashPins >= 2
            PulseOut PORTB.1, 250 ms
        #endif
        #if FlashPins >= 3
            PulseOut PORTB.2, 250 ms
        #endif
        #if FlashPins >= 4
            PulseOut PORTB.3, 250 ms
        #endif
    Loop

Key line: #if FlashPins >= 1 — because FlashPins is 2, this block and the >= 2 block below it are compiled into the program, while the >= 3 and >= 4 blocks are removed entirely at compile time and never take up program memory on the chip.

See Also:

  • #ifnot — the inverse test, compiling code only when the condition is false
  • #ifdef — testing whether a constant is defined, rather than its value
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