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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- S E M _ D I M --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 2011-2018, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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17 -- for more details. You should have received a copy of the GNU General --
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18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
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19 -- http://www.gnu.org/licenses for a complete copy of the license. --
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20 -- --
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21 -- GNAT was originally developed by the GNAT team at New York University. --
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22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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23 -- --
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24 ------------------------------------------------------------------------------
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25
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26 -- This package provides support for numerical systems with dimensions. A
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27 -- "dimension" is a compile-time property of a numerical type which represents
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28 -- a relation between various quantifiers such as length, velocity, etc.
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29
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30 -- Package System.Dim.Mks offers a ready-to-use system of SI base units. In
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31 -- addition, the implementation of this feature offers the ability to define
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32 -- an arbitrary system of units through the use of Ada 2012 aspects.
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33
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34 -- Dimensionality checking is part of type analysis performed by the compiler.
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35 -- It ensures that manipulation of quantified numeric values is sensible with
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36 -- respect to the system of units.
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37
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38 -----------------------------
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39 -- Aspect_Dimension_System --
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40 -----------------------------
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41
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42 -- In order to enable the user to create their own dimension system, a new
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43 -- aspect: Aspect_Dimension_System has been created.
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44
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45 -- Note that this aspect applies for type declaration of type derived from any
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46 -- numeric type.
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47
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48 -- It defines the names of each dimension
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49
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50 ----------------------
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51 -- Aspect_Dimension --
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52 ----------------------
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53
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54 -- This new aspect applies for subtype and object declarations in order to
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55 -- define new dimensions.
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56
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57 -- Using this aspect, the user is able to create new subtype/object with any
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58 -- dimension needed.
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59
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60 -- Note that the base type of the subtype/object must be the type that defines
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61 -- the corresponding dimension system.
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62
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63 -- The expression of this aspect is an aggregate of rational values for each
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64 -- dimension in the corresponding dimension system.
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65
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66 -------------------------------------------
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67 -- Dimensionality checking & propagation --
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68 -------------------------------------------
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69
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70 -- For each node (when needed), a dimension analysis (Analyze_Dimension) is
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71 -- performed as part of the Resolution routine or the Analysis routine if no
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72 -- Resolution.
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73
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74 -- The dimension analysis is divided into two phases:
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75
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76 -- Phase 1: dimension checking
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77
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78 -- Phase 2: propagation of dimensions
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79
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80 -- Depending on the node kind, either none, one phase or two phases are
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81 -- executed.
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82
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83 -- Phase 2 is called only when the node allows a dimension (see body of
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84 -- Sem_Dim to get the list of nodes that permit dimensions).
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85
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86 -- In principle every node that is a component of a floating-point expression
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87 -- may have a dimension vector. However, the dimensionality checking is for
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88 -- the most part a bottom-up tree traversal, and the dimensions of operands
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89 -- become irrelevant once the dimensions of an operation have been computed.
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90 -- To minimize space use, the dimensions of operands are removed after the
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91 -- computation of the dimensions of the parent operation. This may complicate
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92 -- the analysis of nodes that have been constant-folded or otherwise rewritten
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93 -- when removing side effects. In such cases, the (sub)type of the expression
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94 -- is used to determine the applicable dimensions.
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95
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96 with Types; use Types;
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97
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98 package Sem_Dim is
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99
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100 procedure Analyze_Aspect_Dimension
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101 (N : Node_Id;
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102 Id : Entity_Id;
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103 Aggr : Node_Id);
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104 -- Analyze the contents of aspect Dimension. Associate the provided values
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105 -- and quantifiers with the related context N. Id is the corresponding
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106 -- Aspect_Id (Aspect_Dimension) Aggr is the corresponding expression for
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107 -- the aspect Dimension declared by the declaration of N.
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108
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109 procedure Analyze_Aspect_Dimension_System
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110 (N : Node_Id;
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111 Id : Entity_Id;
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112 Aggr : Node_Id);
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113 -- Analyze the contents of aspect Dimension_System. Extract the numerical
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114 -- type, unit name and corresponding symbol from each indivitual dimension.
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115 -- Id is the corresponding Aspect_Id (Aspect_Dimension_System). Aggr is
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116 -- the corresponding expression for the aspect Dimension_System from the
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117 -- declaration of N.
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118
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119 procedure Analyze_Dimension (N : Node_Id);
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120 -- N may denote any of the following contexts:
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121 -- * aggregate
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122 -- * assignment statement
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123 -- * attribute reference
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124 -- * binary operator
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125 -- * call
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126 -- * compontent declaration
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127 -- * extended return statement
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128 -- * expanded name
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129 -- * explicit dereference
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130 -- * identifier
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131 -- * indexed component
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132 -- * number declaration
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133 -- * object declaration
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134 -- * object renaming declaration
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135 -- * procedure call statement
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136 -- * qualified expression
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137 -- * selected component
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138 -- * simple return statement
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139 -- * slice
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140 -- * subtype declaration
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141 -- * type conversion
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142 -- * unary operator
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143 -- * unchecked type conversion
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144 -- Depending on the context, ensure that all expressions and entities
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145 -- involved do not violate the rules of a system.
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146
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147 procedure Analyze_Dimension_Array_Aggregate
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148 (N : Node_Id;
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149 Comp_Typ : Entity_Id);
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150 -- Check, for each component of the array aggregate denoted by N, the
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151 -- dimensions of the component expression match the dimensions of the
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152 -- component type Comp_Typ.
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153
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154 procedure Analyze_Dimension_Call (N : Node_Id; Nam : Entity_Id);
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155 -- This routine is split in two steps. Note the second step applies only to
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156 -- function calls.
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157 -- Step 1. Dimension checking:
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158 -- * General case: check the dimensions of each actual parameter match
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159 -- the dimensions of the corresponding formal parameter.
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160 -- * Elementary function case: check each actual is dimensionless except
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161 -- for Sqrt call.
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162 -- Step 2. Dimension propagation (only for functions):
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163 -- * General case: propagate the dimensions from the returned type to the
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164 -- function call.
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165 -- * Sqrt case: the resulting dimensions equal to half the dimensions of
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166 -- the actual
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167
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168 procedure Analyze_Dimension_Extension_Or_Record_Aggregate (N : Node_Id);
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169 -- Check, for each component of the extension or record aggregate denoted
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170 -- by N, the dimensions of the component expression match the dimensions of
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171 -- the component type.
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172
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173 procedure Analyze_Dimension_Formals (N : Node_Id; Formals : List_Id);
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174 -- For sub spec N, issue a warning for each dimensioned formal with a
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175 -- literal default value in the list of formals Formals.
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176
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177 procedure Check_Expression_Dimensions
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178 (Expr : Node_Id;
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179 Typ : Entity_Id);
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180 -- Compute dimensions of a floating-point expression and compare them with
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181 -- the dimensions of a the given type. Used to verify dimensions of the
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182 -- components of a multidimensional array type, for which components are
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183 -- typically themselves arrays. The resolution of such arrays delays the
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184 -- resolution of the ultimate components to a separate phase, which forces
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185 -- this separate dimension verification.
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186
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187 procedure Copy_Dimensions (From : Node_Id; To : Node_Id);
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188 -- Copy dimension vector of node From to node To. Note that To must be a
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189 -- node that is allowed to contain a dimension (see OK_For_Dimension in
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190 -- body of Sem_Dim).
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191
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192 procedure Copy_Dimensions_Of_Components (Rec : Entity_Id);
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193 -- Propagate the dimensions of the components of a record type T to the
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194 -- components of a record type derived from T. The derivation creates
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195 -- a full copy of the type declaration of the parent, and the dimension
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196 -- information of individual components must be transferred explicitly.
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197
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198 function Dimensions_Match (T1 : Entity_Id; T2 : Entity_Id) return Boolean;
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199 -- If the common base type has a dimension system, verify that two
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200 -- subtypes have the same dimensions. Used for conformance checking.
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201
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202 procedure Eval_Op_Expon_For_Dimensioned_Type
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203 (N : Node_Id;
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204 Btyp : Entity_Id);
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205 -- Evaluate the Expon operator for dimensioned type with rational exponent.
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206 -- Indeed the regular Eval_Op_Expon routine (see package Sem_Eval) is
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207 -- restricted to Integer exponent. This routine deals only with rational
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208 -- exponent which is not an integer if Btyp is a dimensioned type.
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209
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210 procedure Expand_Put_Call_With_Symbol (N : Node_Id);
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211 -- Determine whether N denotes a subprogram call to one of the routines
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212 -- defined in System.Dim.Float_IO or System.Dim.Integer_IO and add an
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213 -- extra actual to the call to represent the symbolic representation of
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214 -- a dimension.
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215
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216 function Has_Dimension_System (Typ : Entity_Id) return Boolean;
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217 -- Return True if type Typ has aspect Dimension_System applied to it
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218
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219 function Is_Dim_IO_Package_Instantiation (N : Node_Id) return Boolean;
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220 -- Return True if N is a package instantiation of System.Dim.Integer_IO or
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221 -- of System.Dim.Float_IO.
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222
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223 function New_Copy_Tree_And_Copy_Dimensions
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224 (Source : Node_Id;
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225 Map : Elist_Id := No_Elist;
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226 New_Sloc : Source_Ptr := No_Location;
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227 New_Scope : Entity_Id := Empty) return Node_Id;
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228 -- Same as New_Copy_Tree (defined in Sem_Util), except that this routine
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229 -- also copies the dimensions of Source to the returned node.
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230
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231 procedure Remove_Dimension_In_Statement (Stmt : Node_Id);
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232 -- Remove the dimensions associated with Stmt
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233
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234 end Sem_Dim;
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