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Index > Main > Integer limit in fasm1

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l4m2



Joined: 15 Jan 2015
Posts: 648
l4m2
It's okay to write
Code:
x = $ffff'ffff'ffff'ffff(64b unsigned/65b signed)    
but not
Code:
rept 1 x:$7fff'ffff {}(32b signed, MAX not avaliable)    
Why it differs? So you can write
Code:
x equ $ffff'ffff'ffff    
but can it be possible to compare x with some other integer?
Post 05 Jan 2017, 18:10
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 7724
Location: Kraków, Poland
Tomasz Grysztar
Yes, fasm's preprocessor is limited to 32-bit signed numbers. Keep in mind that fasm's preprocessor is a separate language on top of the assembler.
Post 05 Jan 2017, 18:18
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l_inc



Joined: 23 Oct 2009
Posts: 881
l_inc
Well, that is not the whole truth. I didn't do a thorough investigation, but it seems the preprocessor can work with wider integers as long as these are intermediate values. As we are talking about comparison here, the following code correctly finds the maximum value of $ffff'ffff'ffff and $1'0000'0000'0000 (equmax from here):
Code:
x equ $ffff'ffff'ffff
y equ $1'0000'0000'0000

m equmax x,y
match v,m { display `v,13,10 }    


That works as long as the computed difference fits into the 32-bit signed range. If not (like if one of the above values was 1 instead), a more generalized version would be needed:
Code:
struc equmax v1*,v2*
{
    restore .
    . equ v1
    rept 1 diff_hi : (v1)shr 30 - (v2)shr 30
    \{
        match =0,diff_hi
        \\{
            rept 1 diff_lo : (v1)and $3fffffff - (v2)and $3fffffff
            \\\{
                match - any,diff_lo
                \\\\{
                    rept 0 \\\\\{
        \\}
        match,
        \\{
            match - any,diff_hi
            \\\{
                match, \\\\{\\\\}
                restore .
                . equ v2
            \\\}
        \\}
    \}
}    

The above macro allows to compare 60-bit values. Any other calculations could be extended this way.

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Post 06 Jan 2017, 01:11
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l4m2



Joined: 15 Jan 2015
Posts: 648
l4m2
l_inc wrote:

Tested.
Code:
x equ $ffff'ffff'ffff
rept 1 t:x shr 40 {}    
complied, which means that prepro. allows large value but not as a loop counter
Post 06 Jan 2017, 02:25
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l4m2



Joined: 15 Jan 2015
Posts: 648
l4m2
So converting from number to int can't use a simple rept but
Code:
match, {
  local f, s, g
  rept 80 \{
    local t, u
    macro f x \\{
      rept 1 tSad-(x)/10) mod 10 + (1-(x)/10) mod 10 \\\{
        match =- u, t \\\\{
          f (x)/10
        \\\\}
      \\\}
      rept 1 tSadx) mod 10 \\\{
        match g, s \\\\{
          s equ g \\\\# t
        \\\\}
      \\\}
    \\}
  \}
  macro numy out, in \{
    s equ /
    g equ in
    rept (1 - ((g))mod 2 - (1+(g))mod 2)/2 \\{
      s equ /-
      g equ -(in)
    \\}
    f g
    match /g, s \\{
      out equ g
    \\}
  \}
}
numy out, $146841654
out    
?(This code may not work if the value is near MAX or MIN)
Post 06 Jan 2017, 03:07
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 7724
Location: Kraków, Poland
Tomasz Grysztar
REPT uses the same expression evaluator as the assembler module, so during the expression evaluation the same rules and limits apply (note that the results of expressions are mostly well defined for any value sizes, only the limitations of implementation cause errors - compare with fasmg implementation of the same evaluator). However where the preprocessor itself operates on numbers, it is limited to 32-bit values, since it was designed this way (the addition of REPT with its use of the assembler's calculator was a late one).
Post 06 Jan 2017, 08:44
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