https://github.com/eeriemyxi/c-rpn-eval

C program that can evaluate postfix arithmetic expressions (Reverse Polish Notation).
https://github.com/eeriemyxi/c-rpn-eval

c evaluator parser postfix rpn

Last synced: 12 months ago
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C program that can evaluate postfix arithmetic expressions (Reverse Polish Notation).

• Host: GitHub
• URL: https://github.com/eeriemyxi/c-rpn-eval
• Owner: eeriemyxi
• License: mit
• Created: 2025-04-05T19:29:29.000Z (about 1 year ago)
• Default Branch: main
• Last Pushed: 2025-04-06T07:48:02.000Z (about 1 year ago)
• Last Synced: 2025-06-12T12:47:52.978Z (about 1 year ago)
• Topics: c, evaluator, parser, postfix, rpn
• Language: C
• Homepage:
• Size: 25.4 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README
  • License: LICENSE

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README

          
C-RPN-EVAL

    This program can evaluate postfix arithmetic expressions (Reverse Polish

    Notation).

    CAUTION: The program is actively under development as of right now. Do not

             expect it to be finished, or to work.

HOW TO RUN

    user:~$ git clone --depth 1 https://github.com/eeriemyxi/c-rpn-eval

    user:~$ cd c-rpn-eval

    user:~$ cc -o rpn src/main.c

    user:~$ ./rpn "1 2 +"

NOTES

    If RPN expression is "a b c + d e * * f g - / + h g ^ -",

    

       ALGORITHM

           * Have a stack for storing tokens.

           

           [ a b c + d e * * f g - / + h g ^ - ]

           * See a, add to stack

           * See b, add to stack

           * See c, add to stack

           [ a (b c +) d e * * f g - / + h g ^ - ]

           * See +, pop last two numbers, a and b, then evaluate -> a + b (k), and add k to stack

           * See d, add to stack

           * See e, add to stack

           [ a k (d e *) * f g - / + h g ^ - ]

           * See *, evaluate d * e (l), add l to stack

           [ a (k l *) f g - / + h g ^ - ]

           * See *, evaluate k * l (m), add m to stack

           * See f, add to stack

           * See g, add to stack

           [ a m (f g -) / + h g ^ - ]

           * See -, evaluate f - g (n), add n to stack.

           [ a (m n /) + h g ^ - ]

           * See /, evaluate m / n (o), add o to stack.

           [ (a o +) h g ^ - ]

           * See +, evaluate a + o (p), add p to stack.

           [ p h g ^ - ]

           * See h, add to stack

           * See g, add to stack

           [ p (h g ^) - ]

           * See ^, evaluate h^g (q), add q to stack.

           [ (p q -) ]

           * See -, evaluate p - q (r), add r to stack.

           [ r ]

               RESULT

               

                   The expression evaluated to r.

AST

    FUNCTIONS

    

        I = INTEGER

        B = BINARY OP

    PROCEDURE

    

        2 1 2 * 3 4 * - -         || []

    

        2 (1 2 *) 3 4 * - -       || [B(I(1) I(2) *)]

    

        2 (1 2 *) (3 4 *) - -     || [B(I(1) I(2) *), B(I(3) I(4) *)]

    

        2 ((1 2 *) (3 4 *) -) -   || [B((I(1) I(2) *) (I(3) I(4) *) -)]

    

        (2 ((1 2 *) (3 4 *) -) -) || [B(I(2) B((I(1) I(2) *) (I(3) I(4) *) -) -)]