RpnCalc

RpnCalc is a small calculator program I wrote in euphoria that handles RPN (reverse polish notation) input. The output of the program is pretty poorly designed. I will design and implement a better one soon hopefully. Anyways, here's the code that I wrote:

{{{include get.e

procedure main() sequence stack integer key,input,switch input=0 switch=0 key=0 stack={}

while key!='q' do key=wait_key() if key>47 and key<58 then

if switch=0 then
- input=key-48 switch=1
elsif switch=1 then
- input=input*10+(key-48)
end if

else

--Explicit push command if key=13 then
- stack=input&stack switch=0
elsif key='q' then
- exit
else
- --Push input onto stack if there's new input if switch=1 then
  - stack=input&stack
  end if --If there are enough stack items to process
  if length(stack)>1 then
  - --Begin commands block if key='+' then
    - stack[2]=stack[2]+stack[1]
    elsif key='-' then
    - stack[2]=stack[2]-stack[1]
    elsif key='*' then
    - stack[2]=stack[2]*stack[1]
    elsif key='/' then
    - stack[2]=stack[2]/stack[1]
    elsif key='^' then
    - stack[2]=power(stack[2],stack[1])
    elsif key='%' then
    - stack[2]=remainder(stack[2],stack[1])
    end if
  else
  - puts(1,"Error: Stack Underflow\n") key='q'
  end if --Pop the stack stack=stack[2..length(stack)] --Reset switch and input switch=0 input=0
end if print(1,stack) puts(1,"\n")

end if end while end procedure

main() }}}

Comments on the code are welcome. I may port the program to some other programming language (I'd really like this for my TI calculator). The program would most likely be MUCH prettier in a lisp or forth type language, but, this was an overnight hack in euphoria, so, that's what it looks like.

Comments

An RPN calculator named RPN83 is already available for the TI-83 calculator, and most HPs support RPN by default. The webpage for RPN83 is at http://patrick.wattle.id.au/cameron/software/ti83/rpn/

I wrote a version in Python, which may be removed if anyone thinks it is just unnecessarily taking up page space!:

   1 import sys
   2 
   3 def isOp(c):
   4    return c in ['+', '-', '*', '/']
   5 
   6 def binOp(a,b,o):
   7    if o=='+':   return a+b
   8    elif o=='-': return a-b
   9    elif o=='*': return a*b
  10    elif o=='/':
  11       try:
  12          return a/b
  13       except ZeroDivisionError:
  14          print "Can't divide by zero!"
  15          sys.exit()
  16          
  17 def evalRPN(expr):
  18    stack = []
  19    for elem in expr:
  20       if isOp(elem):
  21          op = elem
  22          b = stack.pop()
  23          a = stack.pop()
  24          stack.append(binOp(a,b,op))
  25       else:
  26          stack.append(int(elem))
  27    return stack.pop()
  28 
  29 
  30 # Infinite REPL
  31 while True:
  32    expression = raw_input(">> ").split(" ")
  33    print evalRPN(expression)

-- MikeNolan