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float.__mod__ and float.__divmod__ produce incorrect results for negative numbers #777

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0963b67
fix: correct __mod__ and __divmod__ implementations for all float types
pauvrepetit Mar 23, 2026
26a9107
fix: delegate int.__mod__(float) and int.__floordiv__(float) to float…
pauvrepetit Mar 23, 2026
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120 changes: 15 additions & 105 deletions stdlib/internal/types/float.codon
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Original file line number Diff line number Diff line change
Expand Up @@ -96,30 +96,12 @@ class float:
ret double %tmp

@pure
@llvm
def __mod__(a: float, b: float) -> float:
%tmp = frem double %a, %b
ret double %tmp
return a - (a // b) * b

def __divmod__(self, other: float) -> Tuple[float, float]:
mod = self % other
div = (self - mod) / other
if mod:
if (other < 0.0) != (mod < 0.0):
mod += other
div -= 1.0
else:
mod = (0.0).copysign(other)

floordiv = 0.0
if div:
floordiv = div.__floor__()
if div - floordiv > 0.5:
floordiv += 1.0
else:
floordiv = (0.0).copysign(self / other)

return (floordiv, mod)
div = self // other
return (div, self - div * other)

@pure
@llvm
Expand Down Expand Up @@ -567,30 +549,12 @@ class float32:
ret float %tmp

@pure
@llvm
def __mod__(a: float32, b: float32) -> float32:
%tmp = frem float %a, %b
ret float %tmp
return a - (a // b) * b

def __divmod__(self, other: float32) -> Tuple[float32, float32]:
mod = self % other
div = (self - mod) / other
if mod:
if (other < float32(0.0)) != (mod < float32(0.0)):
mod += other
div -= float32(1.0)
else:
mod = float32(0.0).copysign(other)

floordiv = float32(0.0)
if div:
floordiv = div.__floor__()
if div - floordiv > float32(0.5):
floordiv += float32(1.0)
else:
floordiv = float32(0.0).copysign(self / other)

return (floordiv, mod)
div = self // other
return (div, self - div * other)

@pure
@llvm
Expand Down Expand Up @@ -982,30 +946,12 @@ class float16:
ret half %tmp

@pure
@llvm
def __mod__(a: float16, b: float16) -> float16:
%tmp = frem half %a, %b
ret half %tmp
return a - (a // b) * b

def __divmod__(self, other: float16) -> Tuple[float16, float16]:
mod = self % other
div = (self - mod) / other
if mod:
if (other < float16(0.0)) != (mod < float16(0.0)):
mod += other
div -= float16(1.0)
else:
mod = float16(0.0).copysign(other)

floordiv = float16(0.0)
if div:
floordiv = div.__floor__()
if div - floordiv > float16(0.5):
floordiv += float16(1.0)
else:
floordiv = float16(0.0).copysign(self / other)

return (floordiv, mod)
div = self // other
return (div, self - div * other)

@pure
@llvm
Expand Down Expand Up @@ -1343,30 +1289,12 @@ class bfloat16:
ret bfloat %tmp

@pure
@llvm
def __mod__(a: bfloat16, b: bfloat16) -> bfloat16:
%tmp = frem bfloat %a, %b
ret bfloat %tmp
return a - (a // b) * b

def __divmod__(self, other: bfloat16) -> Tuple[bfloat16, bfloat16]:
mod = self % other
div = (self - mod) / other
if mod:
if (other < bfloat16(0.0)) != (mod < bfloat16(0.0)):
mod += other
div -= bfloat16(1.0)
else:
mod = bfloat16(0.0).copysign(other)

floordiv = bfloat16(0.0)
if div:
floordiv = div.__floor__()
if div - floordiv > bfloat16(0.5):
floordiv += bfloat16(1.0)
else:
floordiv = bfloat16(0.0).copysign(self / other)

return (floordiv, mod)
div = self // other
return (div, self - div * other)

@pure
@llvm
Expand Down Expand Up @@ -1700,30 +1628,12 @@ class float128:
ret fp128 %tmp

@pure
@llvm
def __mod__(a: float128, b: float128) -> float128:
%tmp = frem fp128 %a, %b
ret fp128 %tmp
return a - (a // b) * b

def __divmod__(self, other: float128) -> Tuple[float128, float128]:
mod = self % other
div = (self - mod) / other
if mod:
if (other < float128(0.0)) != (mod < float128(0)):
mod += other
div -= float128(1.0)
else:
mod = float128(0.0).copysign(other)

floordiv = float128(0.0)
if div:
floordiv = div.__floor__()
if div - floordiv > float128(0.5):
floordiv += float128(1.0)
else:
floordiv = float128(0.0).copysign(self / other)

return (floordiv, mod)
div = self // other
return (div, self - div * other)

@pure
@llvm
Expand Down
12 changes: 2 additions & 10 deletions stdlib/internal/types/int.codon
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Original file line number Diff line number Diff line change
Expand Up @@ -137,13 +137,8 @@ class int:
ret i64 %tmp

@pure
@llvm
def __floordiv__(self, other: float) -> float:
declare double @llvm.floor.f64(double)
%0 = sitofp i64 %self to double
%1 = fdiv double %0, %other
%2 = call double @llvm.floor.f64(double %1)
ret double %2
return float(self) // other

@pure
@overload
Expand All @@ -169,11 +164,8 @@ class int:
ret double %2

@pure
@llvm
def __mod__(self, other: float) -> float:
%0 = sitofp i64 %self to double
%1 = frem double %0, %other
ret double %1
return float(self) % other

@pure
@overload
Expand Down
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