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Estimated hours taken: 0.75 Add Prolog implementation of float__max, float__min, and float__epsilon. library/Mmake: Add float.nu. library/float.nu.nl: New file.
62 lines
1.9 KiB
Plaintext
62 lines
1.9 KiB
Plaintext
%-----------------------------------------------------------------------------%
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% Copyright (C) 1995 University of Melbourne.
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% This file may only be copied under the terms of the GNU Library General
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% Public License - see the file COPYING.LIB in the Mercury distribution.
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%-----------------------------------------------------------------------------%
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%
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% File: float.nu.nl.
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% Main author: fjh.
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%
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% This file provides a Prolog implementation of `float__min', `float__max',
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% and `float__epsilon'.
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%
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%-----------------------------------------------------------------------------%
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% XXX These definitions are highly platform-dependent.
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% Currently we just hard-wire the definitions for IEEE double precision.
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% This code is written very carefully to avoid bugs and incompatibilities
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% in NU-Prolog and SICStus Prolog:
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%
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% We mustn't write `X = 1.7976931348623157E308', because NU-Prolog
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% has a bug which means that it fails to compile that.
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%
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% We mustn't write `X is 1.7976931348623157 * 10 ** 308', as NU-Prolog
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% wants, because SICStus reports a syntax error.
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%
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% We mustn't write `X is 1.7976931348623157 * exp(10, 308)', as SICStus
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% Prolog wants, because NU-Prolog has a different bug which means that
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% it fails to compile that too.
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%
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% Writing this code was like walking a mine-field... if you change it,
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% be sure to test it on both NU-Prolog and SICStus.
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float__max(X) :-
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% 1.7976931348623157E+308
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( nuprolog ->
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X is 1.79769313486231 * '**'(10, 308)
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;
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Exp = exp(10, 308),
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X is 1.79769313486231 * Exp
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).
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float__min(X) :-
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% 2.2250738585072014E-308
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( nuprolog ->
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X is 2.22507385850720 * '**'(10, -308)
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;
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Exp = exp(10, -308),
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X is 2.22507385850720 * Exp
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).
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float__epsilon(X) :-
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% 1.192092896E-07F
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( nuprolog ->
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X is 1.192092896 * '**'(10, -7)
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;
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Exp = exp(10, -7),
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X is 1.192092896 * Exp
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).
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%-----------------------------------------------------------------------------%
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