CAD_PAREA(1V)

NAME
cad_parea - compute area of polygon

SYNOPSIS
cad_parea [ -i input ] [ -o output ]

DESCRIPTION
cad_parea reads from input (standard input if not given) a series of polygon vertex (x,y) coordinate values and writes to output (standard output if not given) the polygon's area. Lines not beginning with a number are silently skipped. Vertices are assumed to be given in counter-clockwise cyclic order.

HINTS
A hole can be accommodated as a clockwise section connected to the periphery by a line segment traced in both directions.

Disjoint pieces may be connected by a line segment traced in both directions.

EXAMPLE
    $ cad_parea
    # comment
    1 0
    2 0
    2 1
    3 1
    3 2
    2 2
    1 2
    0 2
    0 1
    1 1
    ^D
    4

SEE ALSO
cad_boundp(1).

DIAGNOSTICS
Improperly formatted input produces an error message and terminates cad_parea with non-zero exit status.

cad_parea outputs ``0'' for the area of a degenerate polygon.

AUTHOR
Douglas A. Gwyn, BRL/VLD-VMB