Legacy Document

Inside Macintosh: QuickDraw GX Environment and Utilities /

Chapter 8 - QuickDraw GX Mathematics / QuickDraw GX Mathematics Reference

Mathematical Functions / Fixed-Point Operations

MultiplyDivide

You can use the MultiplyDivide function to multiply two numbers and divide by a third number.

long MultiplyDivide (long multiplicand, long multiplier, 
                     long divisor);

multiplicand

The number to be multiplied by the multiplier.

multiplier

The number by which the multiplicand is multiplied.

divisor

The number by which the product is divided.

function result

The quotient of the product of two numbers and the divisor.

DESCRIPTION

The MultiplyDivide function calculates the quotient of the product of two numbers (parameters multiplicand and multiplier) and a divisor.

The function uses a 64-bit intermediate result to maintain accuracy and to prevent premature overflow. The parameters do not need to all be the same fixed-point format. The operation has a bias of 0 bits; if the divisor is the same format as the multiplier, the result is the same format as the multiplicand. If the divisor is the same format as the multiplicand, the result is in the same format as the multiplier.

SPECIAL CONSIDERATIONS

In the case of overflow, MultiplyDivide pins its result to either the gxPositiveInfinity or gxNegativeInfinity constant.