127776288b
This PR lets the termination argument inference consider negations of Nat comparisons. Fixes #8257.
35 lines
849 B
Text
35 lines
849 B
Text
/-- info: Try this: termination_by xs.length / 2 - i -/
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#guard_msgs in
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def foo (xs : String) (i : Nat) (a b : String.Iterator) : Bool :=
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if xs.length / 2 ≤ i then
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true
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else if a.curr ≠ b.curr then
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false
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else
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foo xs (i + 1) a.next b.prev
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termination_by?
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/-- info: Try this: termination_by xs.length / 2 - i -/
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#guard_msgs in
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def bar (xs : String) (i : Nat) (a b : String.Iterator) : Bool :=
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if i < xs.length / 2 then
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if a.curr ≠ b.curr then
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false
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else
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bar xs (i + 1) a.next b.prev
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else
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true
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termination_by?
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/-- info: Try this: termination_by xs.length / 2 - i -/
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#guard_msgs in
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def baz (xs : String) (i : Nat) (a b : String.Iterator) : Bool :=
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if ¬ (i < xs.length / 2) then
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true
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else
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if a.curr ≠ b.curr then
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false
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else
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baz xs (i + 1) a.next b.prev
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termination_by?
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