3ab2c714ec
the support for mutual structural recursion (new since #4575) is extended so that Lean tries to infer it even without annotations. * The error message when termination checking fails looks quite different now. Maybe a bit better, maybe with more room for improvements. * If there are too many combinations (with an arbitrary cut-off) for a given argument type, it will just give up and ask the user to use `termination_by structural`. * It is now legal to specify `termination_by structural` on not necessarily all functions of a clique; this simply restricts the combinations of arguments that Lean considers. --------- Co-authored-by: Tobias Grosser <tobias@grosser.es>
105 lines
2.7 KiB
Text
105 lines
2.7 KiB
Text
Inferred termination argument:
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termination_by n - i
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Inferred termination argument:
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termination_by xs.size - i
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Inferred termination argument:
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termination_by xs.size - i
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Inferred termination argument:
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termination_by (xs.size - i, ys.size - j)
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Inferred termination argument:
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termination_by (xs.size - i, i - j)
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Inferred termination argument:
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termination_by (xs.size - i, i)
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guessLexDiff.lean:84:4-84:11: error: fail to show termination for
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failure
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with errors
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failed to infer structural recursion:
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Not considering parameter xs of failure:
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it is unchanged in the recursive calls
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Cannot use parameter i:
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failed to eliminate recursive application
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_root_.failure xs i
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Could not find a decreasing measure.
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The arguments relate at each recursive call as follows:
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(<, ≤, =: relation proved, ? all proofs failed, _: no proof attempted)
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i #1 #2 i + i
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1) 85:26-38 = = = =
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2) 85:58-76 ? < _ _
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3) 85:26-38 = = = =
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4) 88:26-42 _ < _ _
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5) 88:26-42 ? ≤ ≤ ?
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6) 88:26-42 _ < _ _
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7) 88:26-42 _ < _ _
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8) 88:26-42 _ < _ _
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9) 97:8-20 _ < _ _
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#1: xs.size - i
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#2: xs.size - (i + 1)
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Please use `termination_by` to specify a decreasing measure.
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guessLexDiff.lean:102:4-102:18: error: fail to show termination for
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mutual_failure
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mutual_failure2
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with errors
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failed to infer structural recursion:
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Not considering parameter xs of mutual_failure:
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it is unchanged in the recursive calls
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Not considering parameter xs of mutual_failure2:
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it is unchanged in the recursive calls
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Cannot use parameters i of mutual_failure and i of mutual_failure2:
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failed to eliminate recursive application
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mutual_failure2 xs i
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Could not find a decreasing measure.
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The arguments relate at each recursive call as follows:
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(<, ≤, =: relation proved, ? all proofs failed, _: no proof attempted)
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Call from mutual_failure to mutual_failure2 at 104:4-24:
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i #1 #2
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i = ? ?
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#3 ? = ?
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Call from mutual_failure to mutual_failure2 at 104:52-78:
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i #1 #2
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i ? _ _
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#3 _ < _
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Call from mutual_failure to mutual_failure2 at 104:4-24:
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i #1 #2
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i _ _ _
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#3 _ = _
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Call from mutual_failure to mutual_failure2 at 111:4-28:
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i #1 #2
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i _ _ _
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#3 _ < _
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Call from mutual_failure to mutual_failure2 at 117:8-28:
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i #1 #2
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i _ _ _
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#3 _ ? _
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Call from mutual_failure2 to mutual_failure at 123:4-23:
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i #3
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i _ _
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#1 _ _
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#2 _ _
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Call from mutual_failure2 to mutual_failure at 123:50-75:
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i #3
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i _ _
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#1 _ _
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#2 _ _
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Call from mutual_failure2 to mutual_failure at 127:4-27:
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i #3
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i _ _
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#1 _ _
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#2 _ _
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Call from mutual_failure2 to mutual_failure at 133:8-27:
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i #3
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i _ _
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#1 _ _
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#2 _ _
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#1: xs.size - i
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#2: xs.size - (i + 1)
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#3: xs.size - i
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Please use `termination_by` to specify a decreasing measure.
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