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Dave Schmenk
41 lines
1.0 KiB
Plaintext
41 lines
1.0 KiB
Plaintext
//
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// YOU'VE ALREADY SEEN SOME OF THE
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// BUILT-IN FUNCTIONS IN PLASMA, NOW
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// IT IS TIME TO DEFINE OUR OWN. THE
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// REAL POWER OF PLASMA COMES FROM
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// FUNCTION DEFINITIONS THAT USE LOCAL
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// VARIABLES, AND THE ABILITY FOR
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// RECURSION - FUNCTIONS THAT CAN CALL
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// THEMSELVES. THE APPLE II DOES LIMIT
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// THESE ABILITIES SOMEWHAT, BUT SOME
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// COMPLEX ALGORITHMS WORK JUST FINE
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// WITH THESE LIMITATION (INCLUDING
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// THE PLASMA COMPILER, ITSELF).
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//
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// A FUNCTION DEFINITION HAS OPTIONAL
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// ARGUMENTS, OPTIONAL LOCAL VARIABLES,
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// AND AN OPTIONAL RETURN VALUE.
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//
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DEF ADD(A, B)
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WORD C
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C = A + B
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RETURN C
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END
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PUTI(ADD(1, 2))
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DONE
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IN THE ABOVE EXAMPLE, THE RETURN COULD
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BE SIMPLIFIED TO "RETURN A + B" BUT
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I WAS TRYING TO SHOW HOW TO USE LOCAL
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VARIABLES. ARRAYS CAN ALSO BE PLACED
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IN THE LOCAL VARIABLES, BUT NOTE THAT
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THE MAXIMUM SIZE OF LOCAL VARIABLES HAS
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TO BE 255 BYTES OR LESS, PER DEFINITION.
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ALSO, DUE TO THE NATURE OF THE 6502 CALL
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STACK, ONLY A CALL DEPTH OF ABOUT 96 IS
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AVAILABLE. AFTER THAT, THE STACK
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OVERFLOWS AND UNEXPECTED THINGS HAPPEN.
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