Complex expressions

[ezgar]

Hi, im triying to learn assembler mainly for curiosity, i have experience in other lenguages like C, C++, Java and C#, but assembler is killing me, it just feels so weird lol, i think is a matter of time to get used to it, right? but well, that´s a completely  different subject; you know, im very used to used to the expressions that high levels lenguages let you make, like i don´t know, like this:

Code Select Expand



someVariable = ( function( bla, bla2, bla3 ) * someValue ) + someOtherValue / function2();



How do you translate that kind of expression in assembler? or something like this:

Code Select Expand



if ( ( anything <= something ) && ( variable1 != variable2 ) || !( function( function3() ) == function2( anotherThing, someOther, lastOne ) ) )
{
    //bla, bla, bla
}



It´s posible to make that kind of things with masm32 in a not so hard way? for example, i know theres a macro called .IF, but it let you make that kind of expressions? do you have to split those expressions in several steps, creating temporal variables or something like that?

Sorry, it´s just that i have programed for years in high level lenguages, and then you try assembler and bam! it´s like a completely different world :D

[drizz]

Hello,

Code Select Expand



someVariable = ( function( bla, bla2, bla3 ) * someValue ) + someOtherValue / function2();



Well, first explain how this expression is evaluated (feel free to use temporary variables in your explanation). If you programmed for years it shouldn't be a problem.

[dedndave]

 :bg
drizz - lol

there are "high-level" expressions in asm, as well - probably not as complex as C allows
i never use them - i prefer to use the lower-level instuctions   :P

[drizz]

Dave, I wasn't trying to be funny. I want him to answer his own question by himself.

[hutch--]

ezgar,

Drizz's approach is the right idea, you must break your code down into bits to do the calculation.

Code Select Expand


// turn this
someVariable = ( function( bla, bla2, bla3 ) * someValue ) + someOtherValue / function2();

// into something like this
rv1 = function2()
rv2 = someothervalue / rv1
rv3 = function(etc)


Then do the calculation.

[Tight_Coder_Ex]

This is just one of the possibilities without using higher level constructs that are available in MASM and some other Assemblers

someVariable = ( function( bla, bla2, bla3 ) * someValue ) + someOtherValue / function2();

Code Select Expand


        push    bla3
        push    bla2
        push    bla
        call    function
        imul    someValue
        mov     someVariable, eax

        call    function2
        mov     ecx, eax
        mov     eax, someOtherValue
        xor     edx, edx
        div     ecx
        add     someVariable, eax

[ezgar]

Ok, thank you all, i know you can always split it into several steps but i was just hoping an easier way to do things, like some magical macro that make the dirty work for you lol (sorry, i just have a couple of days reading about masm32 and i don´t know what let you do and what don´t  :red); i have been playing around with the .IF macro and at least it let you make some complex things.

Thanks again :)

[jj2007]

Search the Forum for solving expressions - there are some threads dealing with your question.

[MichaelW]

ezgar,

A MASM high-level syntax version of your C statement can be not that different from the C. You cannot do direct memory to memory comparisons, so for each such comparison somewhere ahead of the high-level statement you must move one of the variables being compared into an appropriate register. You can use the MASM32 rv macro to effectively substitute EAX, loaded with the return value, for each of the function calls. For MASM a "!" is an operator, but not a logical-not operator, so you will need to change the sense of the equality that follows.

[qWord]

some magical macro that make the dirty work

masm macros can be very powerful, as long as you do the dirty job of programming them   :lol

[jj2007]

For MASM a "!" is an operator, but not a logical-not operator

Michael,

Since this is the Campus, you might need to elaborate on that statement...
:bg

[MichaelW]

For MASM a "!" is the literal-character operator, used to force the assembler to treat the character following it as a literal character instead of a special character. So "!(expression)" will not have the desired not effect :bg

[jj2007]

Michael,
That is true for using ! in strings (and can be confusing...), but the OP used if ( ( anything <= something ) && ( variable1 != variable2 )... - which seems a valid usage of the not operator.

[MichaelW]

This is the part of the original statement that I was referring to:

  !( function( function3() ) == function2( anotherThing, someOther, lastOne ) ) )

[jj2007]

Hmmm....

include \masm32\include\masm32rt.inc

.code
start:
   .if ![/b]rv(HeapAlloc, rv(GetProcessHeap), 0, 1000)
      MsgBox 0, "Could not allocated heap mem, sorry", "Serious problem:", MB_OK
   .else
      invoke HeapFree, rv(GetProcessHeap), 0, eax
      MsgBox 0, "There is heap on your puter", "Hi", MB_OK
   .endif
   exit
end start