92a72b238b
They can be used to store user state in the tactic_state object. @Armael @jroesch: The new file tests/lean/run/tactic_ref.lean contains a few examples.
36 lines
705 B
Text
36 lines
705 B
Text
open tactic
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meta def tst1 (n : nat) : tactic nat :=
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using_new_ref n $ λ r, do
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v ← read_ref r,
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trace v,
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write_ref r (v*2),
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v ← read_ref r,
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trace v,
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return v
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example : true :=
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by do
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v ← tst1 10,
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guard (v = 20),
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constructor
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meta def tst2 : tactic nat :=
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do r ← using_new_ref 0 $ λ r, do {
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return r
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},
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read_ref r -- Should produce an exception, the reference is not valid anymore
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run_cmd fail_if_success $ tst2
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meta def tst3 (n : nat) : tactic nat :=
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using_new_ref n $ λ r,
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(write_ref r (n+10) >> failed) -- The state should be restored during backtracking
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<|>
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(read_ref r)
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example : true :=
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by do
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v ← tst3 10,
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guard (v = 10),
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constructor
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