28906

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(* ID: $Id$


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Authors: Tobias Nipkow, TU Muenchen


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Concrete syntax for floats


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*)


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signature FLOAT_SYNTAX =


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sig


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val setup: theory > theory


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end;


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structure FloatSyntax: FLOAT_SYNTAX =


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struct


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(* parse translation *)


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local


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fun mk_number i =


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let


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fun mk 0 = Syntax.const @{const_name Int.Pls}


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 mk ~1 = Syntax.const @{const_name Int.Min}


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 mk i = let val (q, r) = Integer.div_mod i 2


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in HOLogic.mk_bit r $ (mk q) end;


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in Syntax.const @{const_name Int.number_of} $ mk i end;


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fun mk_frac str =


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let


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val {mant=i, exp = n} = Syntax.read_float str;


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val exp = Syntax.const @{const_name "Power.power"};


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val ten = mk_number 10;


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val exp10 = if n=1 then ten else exp $ ten $ (mk_number n);


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in (Syntax.const @{const_name "divide"}) $ (mk_number i) $ exp10 end


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in


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fun float_tr (*"_Float"*) [t as Const (str, _)] = mk_frac str


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 float_tr (*"_Float"*) ts = raise TERM ("float_tr", ts);


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end;


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(* theory setup *)


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val setup =


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Sign.add_trfuns ([], [("_Float", float_tr)], [], []);


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end;
