117 lines
5.4 KiB
Ada
117 lines
5.4 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- E V A L _ F A T --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2020, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING3. If not, go to --
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-- http://www.gnu.org/licenses for a complete copy of the license. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package provides for compile-time evaluation of static calls to the
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-- floating-point attribute functions. It is the compile-time equivalent of
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-- the System.Fat_Gen runtime package. The coding is quite similar, as are
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-- the subprogram specs, except that the type is passed as an explicit
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-- first parameter (and used via ttypes, to obtain the necessary information
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-- about the characteristics of the type for computing the results.
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with Types; use Types;
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with Uintp; use Uintp;
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with Urealp; use Urealp;
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package Eval_Fat is
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subtype UI is Uint;
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-- The compile time representation of universal integer
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subtype T is Ureal;
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-- The compile time representation of floating-point values
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subtype R is Entity_Id;
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-- The compile time representation of the floating-point root type
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-- The following functions perform the operation implied by their name
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-- which corresponds to the name of the attribute which they compute.
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-- The arguments correspond to the attribute function arguments.
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function Adjacent (RT : R; X, Towards : T) return T;
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function Ceiling (RT : R; X : T) return T;
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function Compose (RT : R; Fraction : T; Exponent : UI) return T;
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function Copy_Sign (RT : R; Value, Sign : T) return T;
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function Exponent (RT : R; X : T) return UI;
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function Floor (RT : R; X : T) return T;
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function Fraction (RT : R; X : T) return T;
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function Leading_Part (RT : R; X : T; Radix_Digits : UI) return T;
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function Model (RT : R; X : T) return T;
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function Pred (RT : R; X : T) return T;
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function Remainder (RT : R; X, Y : T) return T;
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function Rounding (RT : R; X : T) return T;
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function Scaling (RT : R; X : T; Adjustment : UI) return T;
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function Succ (RT : R; X : T) return T;
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function Truncation (RT : R; X : T) return T;
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function Unbiased_Rounding (RT : R; X : T) return T;
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-- The following global declarations are used by the Machine attribute
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type Rounding_Mode is (Floor, Ceiling, Round, Round_Even);
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for Rounding_Mode use (0, 1, 2, 3);
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-- Used to indicate rounding mode for Machine attribute
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-- Note that C code in gigi knows that Round_Even is 3
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-- The Machine attribute is special, in that it takes an extra argument
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-- indicating the rounding mode, and also an argument Enode that is a
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-- node used to post warnings (e.g. if asked to convert a negative zero
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-- on a machine for which Signed_Zeros is False).
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function Machine
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(RT : R;
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X : T;
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Mode : Rounding_Mode;
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Enode : Node_Id) return T;
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procedure Decompose_Int
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(RT : R;
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X : T;
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Fraction : out UI;
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Exponent : out UI;
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Mode : Rounding_Mode);
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-- Decomposes a floating-point number into fraction and exponent parts.
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-- The Fraction value returned is an integer representing the value
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-- Fraction * Scale, where Scale is the value (Machine_Radix_Value (RT) **
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-- Machine_Mantissa_Value (RT)). The value is obtained by using biased
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-- rounding (halfway cases round away from zero), round to even, a floor
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-- operation or a ceiling operation depending on the setting of Mode (see
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-- corresponding descriptions in Urealp).
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end Eval_Fat;
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