#! /bin/sh
# file: pltf		G. Moody	24 February 2002

EXP=
XMIN=
XMAX=
DX=
case $# in
  1) EXP="$1" ;;
  2) EXP="$1"; XMIN=$2 ;;
  3) EXP="$1"; XMIN=$2; XMAX=$3 ;;
  4) EXP="$1"; XMIN=$2; XMAX=$3; DX=$4 ;;
esac

if [ "x$EXP" = "x" ]
then
cat <<!
This program produces a table of a function of x.  It can understand
all of the normal arithmetic operators (use ^ for "to the power of"
and % for "the remainder of"), parentheses, and a few functions:
  s(x)     sine of x (where x is in radians)
  c(x)     cosine of x (where x is in radians)
  a(x)	   arctangent of x (returns result in radians)
  l(x)     natural (base e) logarithm of x
  e(x)     exponential of x
  j(n,x)   n-th order Bessel function of x (where n is an integer)
  sqrt(x)  square root of x (x >= 0

!

echo -n "f(x) = "
read EXP
echo -n "Enter the minimum value of x [-50]: "
read XMIN
echo -n "Enter the maximum value of x [50]: "
read XMAX
echo -n "Enter the increment of x [1]: "
read DX
fi

if [ "x$XMIN" = "x" ]
then
    XMIN=-50
fi
if [ "x$XMAX" = "x" ]
then
    XMAX=50
fi
if [ "x$DX" = "x" ]
then
    DX=1
fi
 
ftable "$EXP" $XMIN $XMAX $DX | \
 bc -l | \
 plt 0 1 -t "f(x) = $EXP" -x x -y "f(x)"