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flat assembler > Windows > [solved] How to add two floating point numbers

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UspenskiyKE



Joined: 28 Sep 2016
Posts: 4
[solved] How to add two floating point numbers
Hello! I am a newbie in assembler language programming area. Help me please to solve my "great problem" Smile
I attempted to write a program which is calculating the sum of the two floating point numbers. It was compiled successfully, but the result of the run was unexpected for me. For example, if the one number is 1.3 and another is 1.8, the sum should be equal to 3.1 But my program returns extremely big number as the sum. This is the text of the program:


Code:
format PE console 4.0
 
include 'include\win32a.inc'
start:  cinvoke printfreq41h   ; Âûâîä íà ýêðàí
    cinvoke scanftptA       ; ââîä A
    cinvoke printf,  req42h   ; Âûâîä íà ýêðàí 
    cinvoke scanftptB       ; ââîä B
    fld  [A]
    fld   [B]
    fadd st0st1
    fst dword [C]

    cinvoke printftpoC
    invoke  sleep50000     ; 50 sec. delay
;
gtfo:   invoke  exit0
req db  'Enter %c:',0
tpo db  'A + B = '
tpt db  '%f',0
A   dd  ?
B   dd  ?
C   dd  ?
; import data in the same section
 data import
 
 library msvcrt,'MSVCRT.DLL',\
    kernel32,'KERNEL32.DLL'
 
 import kernel32,\
    sleep,'Sleep'
 
 import msvcrt,\
    puts,'puts',\
    scanf,'scanf',\
        printf,'printf',\ 
    exit,'exit'
end data



What was my mistake? My CPUs are AMD E2 and Intel Core i3.

Great thanks!

Edit by revolution: Added code tags
Post 21 Nov 2016, 18:43
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system error



Joined: 01 Sep 2013
Posts: 438
I think the printf prints a double. Something like


Code:
push dword[s+4]
push dword[s]
push f
call [printf]
add esp,12

call [getchar]
invoke exit,0

f db '%f',0ah,0
s dq 3.43



Using 32-bit floats may complicate things further (promotion, multiple pushes etc). Try using all doubles for variables and see how it goes. Btw, printf's arguments like variables are passed by values, not by reference. If you are new, my suggestion is to test short codes first especially when dealing with Win API and high-level constructs. They are known to hide things and children.
Post 21 Nov 2016, 21:58
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system error



Joined: 01 Sep 2013
Posts: 438
Ok, here's a wild guess of what you are trying to achieve here


Code:
cinvoke scanf,x,A
cinvoke scanf,x,B
cinvoke getchar   ;for that classic "I can't see the output" cry.

fld qword[A]   ;the thing
fld qword[B]
fadd st0,st1
fstp qword[C]

;Split the double into two unit. printf dont like floats.
cinvoke printf,f,dword[C],dword[C+4]  

cinvoke getchar  ;don't fall asleep!
invoke exit,0

x db '%lf',0   ;double needs a %lf specifier for scanf
f db '%f',0ah,0
A dq ?
B dq ?
C dq ?



I'm not interested in solving it for you but judging by the blasphemy of Win API that you are messing up with, I decided to throw in some clues.
Post 21 Nov 2016, 22:52
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 14590
Location: Planet Dirt
If you include win32ax then you can use the double keyword instead of manually pushing two dwords:

Code:
cinvoke printftpodouble C

Post 22 Nov 2016, 03:12
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UspenskiyKE



Joined: 28 Sep 2016
Posts: 4
Problem solved! Thanks to all!
Post 22 Nov 2016, 08:35
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