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<title>VHDL LRM- Introduction</title>
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<h1><a name="6">Section 6</a></h1>
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<h1>Names</h1>
<p>
<p>The rules applicable to the various forms of name are described in this section.
<h2><a name="6.1"> <a href = "1076_6.HTM#6.1"> 6.1 </a> Names</a></h2>
<p>Names can denote declared entities, whether declared explicitly or implicitly. Names can also denote
<ul>
<p>-- Objects denoted by access values,
<p>-- Subelements of composite objects,
<p>-- Subelements of composite values,
<p>-- Slices of composite objects,
<p>-- Slices of composite values, and
<p>-- Attributes of any named entity.
</ul>
<pre> name ::=
simple_name
| operator_symbol
| selected_name
| indexed_name
| slice_name
| attribute_name
prefix ::=
name
| function_call
</pre>
<p>Certain forms of name (indexed and selected names, slices, and attribute names) include a <i>prefix</i> that is a name or a function call. If the prefix of a name is a function call, then the name denotes an element, a slice, or an attribute, either of the result of the function call, or (if the result is an access value) of the object designated by the result. Function calls are defined in <a href = "1076_7.HTM#7.3.3"> 7.3.3 </a> .
<p>If the type of a prefix is an access type, then the prefix must not be a name that denotes a formal parameter of mode <b>out</b> or a subelement thereof.
<p>A prefix is said to be <i>appropriate</i> for a type in either of the following cases:
<ul>
<p>-- The type of the prefix is the type considered.
<p>-- The type of the prefix is an access type whose designated type is the type considered.
</ul>
<p>The evaluation of a name determines the named entity denoted by the name. The evaluation of a name that has a prefix includes the evaluation of the prefix,that is, of the corresponding name or function call. If the type of the prefix is an access type, the evaluation of the prefix includes the determination of the object designated by the corresponding access value. In such a case, it is an error if the value of the prefix is a null access value. It is an error if,after all type analysis (including overload resolution) the name is ambiguous.
<p>A name is said to be a <i>static</i> <i>name</i> if and only if one of the following conditions holds:
<ul>
<p>-- The name is a simple name or selected name (including those that are expanded names) that does not denote a function call or an object or value of an access type and (in the case of a selected name) whose prefix is a static name.
<p>-- The name is an indexed name whose prefix is a static name, and every expression that appears as part of the name is a static expression.
<p>-- The name is a slice name whose prefix is a static name and whose discrete range is a static discrete range.
</ul>
<p>Furthermore, a name is said to be a <i>locally static name</i> if and only if one of the following conditions hold:
<ul>
<p>-- The name is a simple name or selected name (including those that are expanded names) that is not an alias and that does not denote a function call or an object or a value of an access type and (in the case of a selected name) whose prefix is a locally static name.
<p>-- The name is a simple name or selected name (including those that are expanded names) that is an alias, and that the aliased name given in the corresponding alias declaration (see <a href = "1076_4.HTM#4.3.3"> 4.3.3 </a> ) is a locally static name, and (in the case of a selected name) whose prefix is a locally static name.
<p>-- The name is an indexed name whose prefix is a locally static name, and every expression that appears as part of the name is a locally static expression.
<p>-- The name is a slice name whose prefix is a locally static name and whose discrete range is a locally static discrete range.
</ul>
<p>A <i>static signal name</i> is a static name that denotes a signal. The <i>longest static prefix</i> of a signal name is the name itself, if the name is a static signal name; otherwise, it is the longest prefix of the name that is a static signal name. Similarly, a <i>static variable name</i> is a static name that denotes a variable, and the longest static prefix of a variable name is the name itself, if the name is a static variable name; otherwise, it is the longest prefix of the name that is a static variable name.
<p><i>Examples:</i>
<pre> S(C,2) -- A static name: C is a static constant.
R(J <b>to</b> 16) -- A nonstatic name: J is a signal.
-- R is the longest static prefix of R(J <b>to</b> 16).
T(n) -- A static name; n is a generic constant.
T(2) -- A locally static name.
</pre>
<h2><a name="6.2"> <a href = "1076_6.HTM#6.2"> 6.2 </a> Simple names</a></h2>
<p>A simple name for a named entity is either the identifier associated with the entity by its declaration, or another identifier associated with the entity by an alias declaration. In particular, the simple name for an entity interface, a configuration, a package, a procedure, or a function is the identifier that appears in the corresponding entity declaration, configuration declaration, package declaration, procedure declaration, or function declaration, respectively. The simple name of an architecture is that defined by the identifier of the architecture body.
<pre> simple_name ::= identifier
</pre>
<p>The evaluation of a simple name has no other effect than to determine the named entity denoted by the name.
<h2><a name="6.3"> <a href = "1076_6.HTM#6.3"> 6.3 </a> Selected names</a></h2>
<p>A selected name is used to denote a named entity whose declaration appears either within the declaration of another named entity or within a design library.
<pre> selected_name ::= prefix . suffix
suffix ::=
simple_name
| character_literal
| operator_symbol
| <b>all</b>
</pre>
<p>A selected name may be used to denote an element of a record, an object designated by an access value, or a named entity whose declaration is contained within another named entity, particularly within a library or a package. Furthermore, a selected name may be used to denote all named entities whose declarations are contained within a library or a package.
<p>For a selected name that is used to denote a record element, the suffix must be a simple name denoting an element of a record object or value. The prefix must be appropriate for the type of this object or value.
<p>For a selected name that is used to denote the object designated by an access value, the suffix must be the reserved word <b>all</b>. The prefix must belong to an access type.
<p>The remaining forms of selected names are called <i>expanded names</i>. The prefix of an expanded name may not be a function call.
<p>An expanded name denotes a primary unit contained in a design library if the prefix denotes the library and the suffix is the simple name of a primary unit whose declaration is contained in that library. An expanded name denotes all primary units contained in a library if the prefix denotes the library and the suffix is the reserved word <b>all</b>. An expanded name is not allowed for a secondary unit, particularly for an architecture body.
<p>An expanded name denotes a named entity declared in a package if the prefix denotes the package and the suffix is the simple name, character literal, or operator symbol of a named entity whose declaration occurs immediately within that package. An expanded name denotes all named entities declared in a package if the prefix denotes the package and the suffix is the reserved word <b>all</b>.
<p>An expanded name denotes a named entity declared immediately within a named construct if the prefix denotes a construct that is an entity interface, an architecture, a subprogram, a block statement, a process statement, a generate statement, or a loop statement, and the suffix is the simple name, character literal, or operator symbol of a named entity whose declaration occurs immediately within that construct. This form of expanded name is only allowed within the construct itself.
<p>If, according to the visibility rules, there is at least one possible interpretation of the prefix of a selected name as the name of an enclosing entity interface, architecture, subprogram, block statement, process statement, generate statement, or loop statement, then the only interpretations considered are those of the immediately preceding paragraph. In this case, the selected name is always interpreted as an expanded name. In particular, no interpretations of the prefix as a function call are considered.
<p><i>Examples:</i>
<pre> -- Given the following declarations:
<b>type</b> INSTR_TYPE <b>is</b>
<b>record</b>
OPCODE: OPCODE_TYPE;
<b>end</b> <b>record</b>;
<b>signal</b> INSTRUCTION: INSTR_TYPE;
-- The name "INSTRUCTION.OPCODE" is the name of a record element.
-- Given the following declarations:
<b>type</b> INSTR_PTR <b>is</b> <b>access</b> INSTR_TYPE;
<b>variable</b> PTR: INSTR_PTR;
-- The name "PTR.<b>all</b>" is the name of the object designated by PTR.
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