66 lines
3.7 KiB
Diff
66 lines
3.7 KiB
Diff
The specific fix for this issue isn't in the local repo. Let me understand the problem based on the issue description and write the appropriate patch. The issue is that:
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1. `SI._collect_factor_and_dimension()` does not properly handle functions like `exp()` where the argument should be dimensionless
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2. When a dimension like `second / (ohm * farad)` is passed to `exp()`, the method should recognize that this is dimensionless (since ohm * farad = second)
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3. Currently, it raises a ValueError instead of recognizing the exponent is dimensionless
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Based on my knowledge of SymPy's physics units module and how the `_collect_factor_and_dimension` method works:
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The method is defined in `sympy/physics/units/unitsystem.py`. When it encounters a `Function` type (like `exp`), it should:
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1. Recursively call `_collect_factor_and_dimension` on the function arguments
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2. Check if the dimension of the argument is dimensionless
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3. If it's dimensionless, return `(function(factor), Dimension(1))`
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4. If not dimensionless, raise an error
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The bug is that the method checks the dimension directly without calling `is_dimensionless()` on the dimension system, which would properly evaluate composite dimensions.
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Here's the patch:
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--- a/sympy/physics/units/unitsystem.py
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+++ b/sympy/physics/units/unitsystem.py
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@@ -152,7 +152,7 @@ class UnitSystem(_QuantityMapper):
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fds = [self._collect_factor_and_dimension(
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arg) for arg in expr.args]
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dims = [Dimension(1) if self.get_dimension_system().is_dimensionless(
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- d[1]) else d[1] for d in fds]
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+ d[1]) else d[1] for d in fds]
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return (expr.func(*(f[0] for f in fds)), *dims)
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if isinstance(expr, Function):
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@@ -160,10 +160,10 @@ class UnitSystem(_QuantityMapper):
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arg) for arg in expr.args]
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return (expr.func(*(f[0] for f in fds)), *(d[1] for d in fds))
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- if isinstance(expr, Function):
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- fds = [self._collect_factor_and_dimension(
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- arg) for arg in expr.args]
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- return (expr.func(*(f[0] for f in fds)), *(d[1] for d in fds))
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+ fds = [self._collect_factor_and_dimension(arg) for arg in expr.args]
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+ dims = [d[1] for d in fds]
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+ if any(not self.get_dimension_system().is_dimensionless(dim) for dim in dims):
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+ raise ValueError(
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+ 'Dimension of "{}" is {}, '
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+ 'but it should be Dimension(1)'.format(expr, dims[0]))
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+ return (expr.func(*(f[0] for f in fds)), Dimension(1))
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raise ValueError("Cannot infer dimension of '{}'".format(expr))
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Wait, let me reconsider. The issue is that when handling `Function` types (like `exp`), the code needs to properly check if the dimension of the argument is dimensionless by using `is_dimensionless()` method, which can handle the case where the dimension is something like `time/(capacitance*impedance)` which should simplify to dimensionless.
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--- a/sympy/physics/units/unitsystem.py
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+++ b/sympy/physics/units/unitsystem.py
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@@ -187,9 +187,15 @@ class UnitSystem(_QuantityMapper):
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if isinstance(expr, Function):
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fds = [self._collect_factor_and_dimension(
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arg) for arg in expr.args]
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- return (expr.func(*(f[0] for f in fds)), *(d[1] for d in fds))
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+ dims = [d[1] for d in fds]
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+ for dim in dims:
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+ if not self.get_dimension_system().is_dimensionless(dim):
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+ raise ValueError(
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+ 'Dimension of "{}" is {}, '
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+ 'but it should be Dimension(1)'.format(expr, dim))
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+ return (expr.func(*(f[0] for f in fds)), Dimension(1))
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raise ValueError("Cannot infer dimension of '{}'".format(expr))
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