#!/bin/ksh
# Script name: mycalculator
# Example 10.133

# A simple calculator -- uses the bc command to perform the 
# calculations
# Since the shell performs operations on integers only, 
# this program allows
# you to use floating point numbers by writing to and reading 
# from the bcprogram.

cat << EOF
**************************************************
WELCOME TO THE CALCULATOR PROGRAM
*************************************************
EOF

bc |&     # Open co-process

while true
do
    print "Select one of the operators below "
    cat <<- EOF
	a) +
	s) -
	m) *
	d) /
	e) ^
	EOF
    read op
	case $op in
	a) op="+";;
	s) op="-";;
	m) op="*";;
	d) op="/";;
	e) op="^";;
	*) print "Bad operator"
	continue;;
    esac
    print -p scale=3    # write to the co-process
    print "Please enter two numbers: "  # write to standard out
    read num1 num2      # read from standard in
    print -p "$num1" "$op" "$num2"  #write to the co-process
    read -p result     #read from the co-process
    print $result
    print -n "Continue (y/n)? "
    read answer
    case $answer in
    [Nn]* )
	break;;
    esac
done
print Good-bye