RPN Calculator - v0.02

disclaimer: I copied this from my old blog. Not sure if it actually works:)

My calculator code was quite easily polished up. Here’s the revised code which stacks operands properly and supports the main arithmetic operators +, -, * , /. If you flush the stack completely, you get a “nan” warning, which seems reasonable. Here’s the code: (gas, x86)

.section .data
expr_length:    .int 128
ADD:            .ascii "+"
SUB:            .ascii "-"
MUL:           .ascii "*"
DIV:            .ascii "/"
null:           .ascii "\0"
disp_float:     .ascii "%f\n\n\0"
.section .bss
    .lcomm expr, 128
.section .text
.globl main

main:
    finit
    1:
    leal    null, %esi          #Clear the expr buffer
    leal    expr, %edi
    movl    expr_length, %ecx
    cld
    lodsb
    rep     stosb
    addl    $4, %esp
    pushl   stdin               # Read an expression
    pushl   $64
    pushl   $expr
    call    fgets
    addl    $12, %esp

    movb    ADD, %ah            # Test For Operators
    movb    expr, %bh
    cmp     %ah, %bh
    je      addFloat
    movb    SUB, %ah
    cmp     %ah, %bh
    je      subFloat
    movb    MUL, %ah
    cmp     %ah, %bh
    je      mulFloat
    movb    DIV, %ah
    cmp     %ah, %bh
    je      divFloat

    pushl   $expr               # Must be a number
    call    atof
    addl    $4, %esp
    jmp 1b

    addFloat:
        faddp
        fstl   (%esp)
        jmp     disp_answer

    subFloat:
        fsubrp
        fstl   (%esp)
        jmp     disp_answer

    mulFloat:
        fmulp
        fstl    (%esp)
        jmp     disp_answer

    divFloat:
        fdivrp
        fstl   (%esp)

    disp_answer:
        pushl   $disp_float
        call    printf
        addl    $8, %esp
        jmp     1b


    notfound:
    movl $1, %eax
    movl $0, %ebx
    int $0x80