95 lines
4.8 KiB
Ada
95 lines
4.8 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S Y S T E M . V A L U E _ F --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 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. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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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 contains the routines for supporting the Value attribute for
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-- ordinary fixed point types whose Small is the ratio of two Int values, and
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-- also for conversion operations required in Text_IO.Fixed_IO for such types.
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generic
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type Int is range <>;
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type Uns is mod <>;
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with procedure Scaled_Divide
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(X, Y, Z : Int;
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Q, R : out Int;
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Round : Boolean);
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package System.Value_F is
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pragma Preelaborate;
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function Scan_Fixed
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(Str : String;
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Ptr : not null access Integer;
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Max : Integer;
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Num : Int;
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Den : Int) return Int;
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-- This function scans the string starting at Str (Ptr.all) for a valid
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-- real literal according to the syntax described in (RM 3.5(43)). The
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-- substring scanned extends no further than Str (Max). There are three
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-- cases for the return:
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--
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-- If a valid real literal is found after scanning past any initial spaces,
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-- then Ptr.all is updated past the last character of the literal (but
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-- trailing spaces are not scanned out). The value returned is the value
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-- Int'Integer_Value (decimal-literal-value), using the given Num/Den to
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-- determine this value.
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--
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-- If no valid real literal is found, then Ptr.all points either to an
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-- initial non-digit character, or to Max + 1 if the field is all spaces
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-- and the exception Constraint_Error is raised.
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--
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-- If a syntactically valid integer is scanned, but the value is out of
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-- range, or, in the based case, the base value is out of range or there
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-- is an out of range digit, then Ptr.all points past the integer, and
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-- Constraint_Error is raised.
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--
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-- Note: these rules correspond to the requirements for leaving the
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-- pointer positioned in Text_Io.Get
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--
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-- Note: if Str is null, i.e. if Max is less than Ptr, then this is a
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-- special case of an all-blank string, and Ptr is unchanged, and hence
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-- is greater than Max as required in this case.
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function Value_Fixed
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(Str : String;
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Num : Int;
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Den : Int) return Int;
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-- Used in computing X'Value (Str) where X is an ordinary fixed-point type.
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-- Str is the string argument of the attribute. Constraint_Error is raised
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-- if the string is malformed or if the value is out of range of Int (not
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-- the range of the fixed-point type, which must be done by the caller).
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-- Otherwise the value returned is the value Int'Integer_Value
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-- (decimal-literal-value), using Small Num/Den to determine this value.
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end System.Value_F;
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