Math in PostScript

5.7 Math in PostScript

The PostScript interpreter can be used as a basic calculator. There are some limits here, however, since it only works with 5 digits of acurracy. After all, how accurate do you need to be when describing coordinates on a page?

There are actually two types of numbers in PostScript, integers and reals. Integers are signed and reals are expressed in the usual mantissa E exponent fashion, such as 2.34E32. Type conversions are usually done for you; you divide and integer by a real with the same command that divides a real by a real. This shouldn't ever cause you any difficulty.

You should probably know something about PostScript's trigonometric functions. PostScript has only three trig functions: atan, cos, and sin. These are sufficient to generate any other trig function, however. For example, you could find the arcsine of 1/2 as in the following ghostscript session 

GS>.5
GS<1>dup
GS<2>2
GS<3>exp
GS<2>1
GS<3>sub
GS<2>neg
GS<2>sqrt
GS<2>atan
GS<1>=
30.0
Notice that the answer is in degrees. This is true for all trig functions: they expect arguments in degrees and they express angles in degrees.

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David Maxwell, who is still writing this, would like to hear your comments and suggestions. And remember, parts of this manual are based on P.J. Weingartner's work: A First Guide to PostScript.