#!/usr/bin/env etsh
:
: etsh - " Force sh(1), csh(1), and other shells to exit w/ error! " <'' ;;;
:
: "  @(#)$Id: c6d78a3c9df262cb840344ebd9aaf68a154c0281 $  "
:
: "  The author of this file, J.A. Neitzel <jan (at) etsh (dot) io>,  "
: "  hereby grants it to the public domain.                           "
:

:
: "  Calculate 3 unknown values representing the size of a circle  "
: "  starting from 1 known value which is specified by the user.   "
: "  Print the resulting values of the area, circumference,        "
: "  diameter, and radius to the standard output.                  "
:
: "  usage: circalc {-a | -c | -d | -r} number  "
:

:
: " Check for correct usage. "
:
: >>$0'' <'' ; : >>$1'' <'' ; : >>$2'' <''
killer $0 circalc
if $# != 2 -o ! \( \
	X$1 = X-a -o X$1 = X-c -o X$1 = X-d -o X$1 = X-r \
\) if { exit } pusage $0 '"{-a | -c | -d | -r} number"'

:
: " Ensure that $2 is either an integer or a floating-point number. "
:
echo $2 | egrep '^(0|0\.[0-9]+|[1-9][0-9]*|[1-9][0-9]*\.[0-9]+)$' >/dev/null
if $? != 0 if { exit } perror $0 $2'": Not a number >= 0"'
if X$1 != X-a goto $1
: fallthrough

: -a - " Solve circumference, diameter, and radius from area. "

	echo    '         Area:  '$2
	echo -n 'Circumference:  '
	echo 'scale = 5 ; 3.14159 * 2 * sqrt ( '$2' / 3.14159 )' | bc
	echo -n '     Diameter:  '
	echo 'scale = 5 ; 2 * sqrt ( '$2' / 3.14159 )' | bc
	echo -n '       Radius:  '
	echo 'scale = 5 ; sqrt ( '$2' / 3.14159 )' | bc
	exit

: -c - " Solve diameter, radius, and area from circumference. "

	echo -n '         Area:  '
	echo 'scale = 5 ; 3.14159 * ( '$2' / ( 3.14159 * 2 ) ) ^ 2' | bc
	echo    'Circumference:  '$2
	echo -n '     Diameter:  '
	echo 'scale = 5 ; '$2' / 3.14159' | bc
	echo -n '       Radius:  '
	echo 'scale = 5 ; '$2' / ( 3.14159 * 2 )' | bc
	exit

: -d - " Solve circumference, radius, and area from diameter. "

	echo -n '         Area:  '
	echo 'scale = 5 ; 3.14159 * ( '$2' / 2 ) ^ 2' | bc
	echo -n 'Circumference:  '
	echo 'scale = 5 ; 3.14159 * 2 * ( '$2' / 2 )' | bc
	echo    '     Diameter:  '$2
	echo -n '       Radius:  '
	echo 'scale = 5 ; '$2' / 2' | bc
	exit

: -r - " Solve circumference, diameter, and area from radius. "

	echo -n '         Area:  '
	echo 'scale = 5 ; 3.14159 * '$2' ^ 2' | bc
	echo -n 'Circumference:  '
	echo 'scale = 5 ; 3.14159 * 2 * '$2 | bc
	echo -n '     Diameter:  '
	echo 'scale = 5 ; 2 * '$2 | bc
	echo    '       Radius:  '$2