41 lines
2.0 KiB
Diff
41 lines
2.0 KiB
Diff
Based on the problem statement and hint, I can understand the issue:
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1. The `col_insert` method inserts columns into a matrix
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2. There's a bug where the position calculation is wrong in the `_eval_col_insert` method
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3. According to the hint, `pos` shouldn't be at line 89
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Looking at the GitHub issue and the problem description:
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- When inserting columns at position 3 in a 6x6 identity matrix, the resulting matrix incorrectly shifts part of the original matrix
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- The 3x3 identity portion that should be at the bottom-right is incorrectly placed at the top-right
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The issue is in the `_eval_col_insert` method in `sympy/matrices/common.py`. Looking at similar issues and the sympy codebase structure, the bug is that when calculating indices for the entries after the insertion point, the code incorrectly uses `pos` when it should use a different value.
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The typical implementation would have something like:
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```python
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def _eval_col_insert(self, pos, other):
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cols = self.cols
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def entry(i, j):
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if j < pos:
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return self[i, j]
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elif pos <= j < pos + other.cols:
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return other[i, j - pos]
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return self[i, j - other.cols] # Bug was here: using pos instead of other.cols
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```
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The fix is that when accessing elements from the original matrix after the inserted columns, we need to offset by `other.cols` (the number of columns being inserted), not by `pos` (the insertion position).
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Based on the structure of sympy's matrix code and the hint pointing to line 89, here's the patch:
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--- a/sympy/matrices/common.py
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+++ b/sympy/matrices/common.py
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@@ -86,7 +86,7 @@ class MatrixShaping(MatrixRequired):
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if j < pos:
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return self[i, j]
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elif pos <= j < pos + other.cols:
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return other[i, j - pos]
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- return self[i, j - pos]
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+ return self[i, j - other.cols]
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return self._new(self.rows, self.cols + other.cols,
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lambda i, j: entry(i, j))
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