19 lines
329 B
Text
19 lines
329 B
Text
import system.io
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inductive token
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| eof : token
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| plus : token
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| var : string -> token
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open token
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open option
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def to_token : list char → option token
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| [] := none
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| (c :: cs) :=
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let t : option token := match c with
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| 'x' := some (var "x")
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| 'y' := some (var "y")
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| '+' := some plus
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| _ := none
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end in t
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