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Fix _mod function to fix the % operator results #1567

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Fix _mod function to fix the % operator results #1567

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seifkosbar
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Closing 1562

Task List:

  • Replaced the _lpython_floordiv function in all the _mod function with _floor function I created based on the math.floor function.

On Branch:

def f():
    print((8)%3)
    print((8)%(3))
    print(-(8)%3)       
    print((8)%-3)          
    print(-(8)%-3)
    print((-8)%3)          
    print(-8%3)            
    
f()

(base) seif@seif:~/Documents/GSoC/lpython$ ./src/bin/lpython examples/try.py
2
2
1
-1
-2
1
1

faze-geek
faze-geek reviewed Mar 8, 2023
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src/lpython/semantics/python_comptime_eval.h Outdated
@@ -212,7 +212,7 @@ struct PythonIntrinsicProcedures {
int64_t a = ASR::down_cast<ASR::IntegerConstant_t>(arg1)->m_n;
int64_t b = ASR::down_cast<ASR::IntegerConstant_t>(arg2)->m_n;
return ASR::down_cast<ASR::expr_t>(
ASR::make_IntegerConstant_t(al, loc, a%b, type));
ASR::make_IntegerConstant_t(al, loc, ((a%b)+b)%b, type));
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Hi, I have handled the compile time evaluations in my pr #1566 and got reviews on it. Could you please remove it from here to avoid clashes.
Also _mod function in lpython_builtin.py works on runtime evaluations, something like this -

def f():
    a:i32 = 8
    b:i32 = -3
    print(a%b)

f()

I hope you are aware of that, since all the test cases you refer in the OP are not in that format. Checkout if outputs of the print(a%b) format are actually getting corrected by the changes you made in lpython_builtin.py . On face value I can see that the below case is handled incorrectly -

def f():
    a:i32 = 8
    b:i32 = 0
    print(a%b)

f()
(lp) C:\Users\kunni\lpython>python try.py
Traceback (most recent call last):
  File "C:\Users\kunni\lpython\try.py", line 6, in <module>
    f()
  File "C:\Users\kunni\lpython\try.py", line 4, in f
    print(a%b)
ZeroDivisionError: integer division or modulo by zero

(lp) C:\Users\kunni\lpython>src\bin\lpython try.py
8

@seifkosbar
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My bad I didn't see your PR, I removed it.

However, thank you for letting me know about the format of the test case. The test case in the OP is the one used in #1562 so I was just trying to test against it again.

I did some edits to handle the case mentioned in your comment:

def f():
    a:i32 = 8
    b:i32 = 0
    print(a%b)

f()

I made _mod function to raise ZeroDivisionError if the divisor is 0. Also, I got the _lpython_floordiv back as the _floor function made the tests to fail.

@overload
def _mod(a: i32, b: i32) -> i32:
    if b == i32(0):
        raise ZeroDivisionError("Integer division or modulo by zero not possible")
    return a - _lpython_floordiv(a, b)*b

I got this:

(lp) seif@seif:~/Documents/GSoC/lpython$ ./src/bin/lpython examples/try.py
ERROR STOP

I am not sure yet why it is behaving like this but I am looking into it.

@faze-geek
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I got this:

(lp) seif@seif:~/Documents/GSoC/lpython$ ./src/bin/lpython examples/try.py
ERROR STOP

I am not sure yet why it is behaving like this but I am looking into it.

Yes, a bit strange. I got the same message on trying out your diff. @Thirumalai-Shaktivel I had pointed this out on zulip recently, Can you look into it !?

czgdp1807
czgdp1807 requested changes Mar 9, 2023
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Add a test in integration_tests folder for this.

@czgdp1807 czgdp1807 marked this pull request as draft March 9, 2023 17:26
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@czgdp1807 czgdp1807 czgdp1807 requested changes

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@seifkosbar @faze-geek @czgdp1807