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researchv10 Dan Cross

.ds ZZ DEVELOPMENT PACKAGE
.TH PTARITH 3R "630 MTG"
.XE "add()"
.XE "sub()"
.XE "mul()"
.XE "div()"
.SH NAME
ptarith: add, sub, mul, div \- arithmetic on Points
.SH SYNOPSIS
.ft B
#include <dmd.h>
.sp
Point add (p, q)
.sp
Point sub (p, q) 
.sp
Point mul (p, a)
.sp
Point div (p, a)
.sp
Point p, q;
.br
int a;
.SH DESCRIPTION
The
.I add
function
returns the Point sum of its arguments:
.sp
.ce
.ft CM
{ p.x+q.x, p.y+q.y }
.sp
.ft R
The
.I sub
function
returns the Point difference of its arguments:
.sp
.ce
.ft CM
{ p.x-q.x, p.y-q.y }
.sp
.ft R
The
.I mul
function
returns the Point:
.sp
.ce
.ft CM
{ p.x*a, p.y*a }
.sp
.ft R
The
.I div
function
returns the Point:
.sp
.ce
.ft CM
{ p.x/a, p.y/a }.
.sp
.ft R
.SH EXAMPLE
The following routine returns the center Point of a \f2window\f1.
.PP
.RS 3
.nf
.ft CM
#include <dmd.h>
Point add();
Point sub();
Point div();
Point
getcenter()
{
    Point offset;
    offset = div (sub
        (Drect.corner,Drect.origin), 2);
    return add (Drect.origin, offset);
}
\fR
.fi
.RE
.SH SEE ALSO
globals(3R), rectarith(3R),  transform(3R/3L).

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