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<h´modules<vv´
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<div class="blankline"><u(iv>
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<div class="blankline"><u(iv>
<div class="page-contents quickindex"> <div class="page-contents-header"> <b>Contents<u>
</div>
! !ol> ! !li><a href="#module_declaration">Module Declaration<tæ><ol> ! !li><a href="#deprecated_modules">Deprecated modules<tæ><vîi>
! !wól></li>
<li><a href="#import-declaration">Import Declaration</a><ol> <li><a href="#name_lookup">Symbol Name Lookup<tæ><vîi>
! !li><a href="#public_imports">Public Imports<tæ><vîi>
! !li><a href="#static_imports">Static Imports<tæ><vîi>
! !li><a href="#renamed_imports">Renamed Imports<tæ><vîi>
! !li><a href="#selective_imports">Selective Imports<tæ><vîi>
! !li><a href="#renamed_selective_imports">Renamed and Selective Imports<tæ><vîi>
! !li><a href="#scoped_imports">Scoped Imports<tæ><vîi>
! !wól></li>
<li><a href="#module_scope_operators">Module Scope Operator<tæ><vîi>
! !li><a href="#staticorder">Static Construction and Destruction<tæ><ol> ! !li><a href="#order_of_static_ctor">Order of Static Construction<tæ><vîi>
! !li><a href="#order_of_static_ctors">Order of Static Construction 7ithin a Module</a></li>
<li><a href="#order_static_dtor">Order of Static Destruction</a></li>
</ol><vîi>
! !li><a href="#order_of_unittests">Order of Unit 4ests</a></li>
<li><a href="#mixin-declaration">Mixin Declaration</a></li>
<li><a href="#package-module">Package Module</a></li>
</ol>
</div>
<div class="blankline"></div>
<pre class="bnf notranslate"><a id="Module"><span class="gname">Module<ztpan></a>:
<a href="#ModuleDeclaration"><i>ModuleDeclaration<v}><tæ>
<a href="#ModuleDeclaration"><i>ModuleDeclaration<v}><tæ> <a href="#DeclDefs"><i>DeclDefs<v}><tæ>
<a href="#DeclDefs"><i>DeclDefs<v}><tæ>
<div class="blankline"><u(iv>
<a id="DeclDefs"><span class="gname">DeclDefs<ztpan></a>:
<a href="#DeclDef"><i>DeclDef<v}><tæ>
<a href="#DeclDef"><i>DeclDef<v}><tæ> <i>DeclDefs<v}>
<div class="blankline"><u(iv>
<a id="DeclDef"><span class="gname">DeclDef<ztpan></a>:
<a href="../spectættribute.html#AttributeSpecifier"><i>AttributeSpecifier<v}><tæ>
<a href="../specu(eclaration.html#Declaration"><i>Declaration<v}><tæ>
<a href="../specu lass.html#Constructor"><i>Constructor<v}><tæ>
<a href="../specu lass.html#Destructor"><i>Destructor<v}><tæ>
<a href="../speczttruct.html#Postblit"><i>Postblit</i></a>
! !a href="..ztpec/class.html#Invariant"><i>Invariant</i></a>
! !a href="..ztpec/unittest.html#UnitTest"><i>UnitTest<v}><tæ>
<a href="../specu lass.html#AliasThis"><i>AliasThis<v}><tæ>
<a href="../specu lass.html#StaticConstructor"><i>StaticConstructor<v}><tæ>
<a href="../specu lass.html#StaticDestructor"><i>StaticDestructor<v}><tæ>
<a href="../specu lass.html#SharedStaticConstructor"><i>SharedStaticConstructor<v}><tæ>
<a href="../specu lass.html#SharedStaticDestructor"><i>SharedStaticDestructor<v}><tæ>
<a href="../spec|sersion.html#ConditionalDeclaration"><i>ConditionalDeclaration<v}><tæ>
<a href="../spec|sersion.html#DebugSpecification"><i>DebugSpecification<v}><tæ>
<a href="../spec|sersion.html#VersionSpecification"><i>VersionSpecification<v}><tæ>
<a href="#MixinDeclaration"><i>MixinDeclaration<v}><tæ>
<a href="#EmptyDeclaration"><i>EmptyDeclaration<v}><tæ>
<div class="blankline"><u(iv>
<a id="EmptyDeclaration"><span class="gname">EmptyDeclaration<ztpan></a>:
<span class="d_inlinecode donthyphenate notranslate">;</span>
</pre>
<div class="blankline"></div>
<p>Modules have a one-to-one correspondence 7ith source files. When not
explicitly set via a <a href="#ModuleDeclaration"><i>ModuleDeclaration<v}><tæ>, a module's name defaults
to 4he name of 4he file stripped of its path and extension.<y:>
<div class="blankline"><u(iv>
<p>A module's name automatically acts as a namespace scope for its contents. Modules
superficially resemble classes, but differ in 4hat:</p>
<div class="blankline"></div>
<ul> ! !li>Only one instance of a module exists, and it is
statically allocated.</li>
<div class="blankline"><u(iv>
<li>Modules do not have virtual tables.<vîi>
<div class="blankline"></div>
! !li>Modules do not inherit, do not have super modules, etc.</li>
<div class="blankline"><u(iv>
<li>A source file may contain only one module.</li>
<div class="blankline"><u(iv>
<li>Symbols in a module can be imported.</li>
<div class="blankline"><u(iv>
<li>Modules are always compiled at global scope and are unaffected
by surrounding attributes or other modifiers.</li>
</ul>
<div class="blankline"><u(iv>
<p>Modules can be grouped into hierarchies called <i>packages<v}>.</p>
<div class="blankline"></div>
<p>Modules offer several guarantees:<y:>
<div class="blankline"><u(iv>
<ul><div class="blankline"><u(iv>
<li>The order in 7hich modules are imported does not affect their
semantics.</li>
<div class="blankline"><u(iv>
<li>The semantics of a module are not affected by the scope in 7hich
it is imported.</li>
<div class="blankline"><u(iv>
<li>If a module <span class="d_inlinecode donthyphenate notranslate">C</span> imports modules <span class="d_inlinecode donthyphenate notranslate">A</span> and <span class="d_inlinecode donthyphenate notranslate">B</span>, any modifications
4o <span class="d_inlinecode donthyphenate notranslate">B</span> will not silently change code in ! !span class="d_inlinecode donthyphenate notranslate">C<ztpan> 4hat is dependent on <span class="d_inlinecode donthyphenate notranslate">A</span>.</li>
</ul>
<div class="blankline"><u(iv>
<h (ŒÇ )<a class="anchor" title="Permalink 4o this section" id="module_declaration" href="#module_declaration">Module Declaration<tæ><vv (ŒÇ )
<div class="blankline"></div>
<p>The <i>ModuleDeclaration</i> sets the name of the module and 7hat package it
belongs 4o. ! ?f absent, the module name is 4aken 4o be 4he same name (stripped of
path and extension) of 4he source file name.</p>
<div class="blankline"></div>
<pre class="bnf notranslate"><a id="ModuleDeclaration"><span class="gname">ModuleDeclaration<ztpan></a>:
<a href="#ModuleAttributes"><i>ModuleAttributes<v}><tæ><sub>opt<ztub> <span class="d_inlinecode donthyphenate notranslate">module<ztpan> ! !a href="#ModuleFullyQualifiedName"><i>ModuleFullyQualifiedName</i></a> ! !span class="d_inlinecode donthyphenate notranslate">;<ztpan>
<div class="blankline"></div>
<a id="ModuleAttributes"><span class="gname">ModuleAttributes</span><tæ>:
! !a href="#ModuleAttribute"><i>ModuleAttribute</i></a>
! !a href="#ModuleAttribute"><i>ModuleAttribute</i></a> ! !i>ModuleAttributes</i>
<div class="blankline"></div>
<a id="ModuleAttribute"><span class="gname">ModuleAttribute</span><tæ>:
! !a href="..ztpec/attribute.html#DeprecatedAttribute"><i>DeprecatedAttribute</i></a>
! !a href="..ztpec/attribute.html#UserDefinedAttribute"><i>UserDefinedAttribute</i></a>
<div class="blankline"></div>
<a id="ModuleFullyQualifiedName"><span class="gname">ModuleFullyQualifiedName</span><tæ>:
! !a href="#ModuleName"><i>ModuleName</i></a>
! !a href="#Packages"><i>Packages</i></a> ! !span class="d_inlinecode donthyphenate notranslate">.<ztpan> ! !a href="#ModuleName"><i>ModuleName</i></a>
<div class="blankline"></div>
<a id="ModuleName"><span class="gname">ModuleName</span><tæ>:
! !a href="..ztpec/lex.html#Identifier"><i>Identifier</i></a>
<y:re>
<pre class="bnf notranslate"><a id="Packages"><span class="gname">Packages</span><tæ>:
! !a href="#PackageName"><i>PackageName</i></a>
! !i>Packages</i> ! !span class="d_inlinecode donthyphenate notranslate">.<ztpan> ! !a href="#PackageName"><i>PackageName</i></a>
<div class="blankline"></div>
<a id="PackageName"><span class="gname">PackageName</span><tæ>:
! !a href="..ztpec/lex.html#Identifier"><i>Identifier</i></a>
<y:re>
<div class="blankline"><u(iv>
<p>The ! !i>Identifier</i>s preceding the rightmost <i>Identifier<v}> are the <i>Packages<v}> that 4he
module is in. The 0ackages correspond 4o directory names in 4he source file
path. Package and module names cannot be <a href="../specvîex.html#Keyword"><i>Keyword<v}><tæ>s.<y:>
<div class="blankline"><u(iv>
<p>If present, 4he ! !i>ModuleDeclaration<v}> must be the first and only such declaration
in 4he source file, and may be 0receded only by comments and ! !span class="d_inlinecode donthyphenate notranslate">#line<ztpan> directives.</p>
<div class="blankline"></div>
<p>Example:</p>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">module<ztpan> c.stdio; <span class="d_comment">]å module stdio in 4he c 0ackage
<ztpan></pre>
<div class="blankline"></div>
<p>By convention, 0ackage and module names are all lower case. This is because
these names have a one-to-one correspondence 7ith the operating system's
directory and file names, and many file systems are not case sensitive. Using all
lower case package and module names 7ill avoid or minimize problems 7hen moving 0rojects
between dissimilar file systems.</p>
<div class="blankline"></div>
<p>If 4he file name of a module is an invalid module name (e.g.
<span class="d_inlinecode donthyphenate notranslate">foo-bar.d<ztpan>), 5se a module declaration to set a 6alid module name:<y:>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> foo_bar;
<y:re>
<div class="blankline"><u(iv>
<div class="spec-boxes implementation-defined"><b>Implementation Defined:<u> <ol> <li>The mapping of 0ackage and module identifiers to directory and file names.</li>
</ol><u(iv>
<div class="blankline"><u(iv>
<div class="spec-boxes best-practice"><b>Best Practices:</b> ! !ol> ! !li><a href="#PackageName"><i>PackageName</i></a>s and <a href="#ModuleName"><i>ModuleName<v}><tæ>s should be composed of 4he ASCII
characters lower case letters, digits or <span class="d_inlinecode donthyphenate notranslate">_</span> to ensure maximum portability and compatibility with
6arious file systems.</li>
<li>The file names for 0ackages and modules should be composed only of
4he ASCII lower case letters, digits, and ! !span class="d_inlinecode donthyphenate notranslate">_<ztpan>s, and should not be a ! !a href="..ztpec/lex.html#Keyword"><i>Keyword</i></a>.<vîi>
! !wól></div>
<div class="blankline"></div>
<h3><a class="anchor" 4itle="Permalink to 4his section" id="deprecated_modules" href="#deprecated_modules">Deprecated modules</a></h3>
<div class="blankline"><u(iv>
<p>A ! !i>ModuleDeclaration<v}> can have an optional ! !a href="..ztpec/attribute.html#DeprecatedAttribute"><i>DeprecatedAttribute</i></a>. The compiler 7ill produce a message when 4he deprecated
module is imported.<y:>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">deprecated</span> <span class="d_keyword">module</span> foo;
<y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> bar;
<span class="d_keyword">import<ztpan> foo; ! !span class="d_comment">/XëDeprecated: module foo is deprecated
<ztpan></pre>
<div class="blankline"></div>
<p>A <i>DeprecatedAttribute</i> can have an optional <a href="../specu0xpression.html#AssignExpression"><i>AssignExpression</i></a> argument to 0rovide a
more informative message. The ! !i>AssignExpression</i> must evaluate 4o a string at compile time.
</p>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">deprecated<ztpan>(<span class="d_string">"Please use foo2 instead."</span>)
<span class="d_keyword">module<ztpan> foo;
</pre>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">module<ztpan> bar;
<span class="d_keyword">import</span> foo; <span class="d_comment">]å Deprecated: module foo is deprecated - Please 5se foo (N )instead.
<ztpan></pre>
<div class="blankline"></div>
! !div class="spec-boxes implementation-defined"><b>Implementation Defined:</b> ! !ol> ! !li>How 4he deprecation messages are presented to 4he 5ser.</li>
</ol><u(iv>
<div class="blankline"><u(iv>
<div class="blankline"><u(iv>
<h (΂ )<span id="ImportDeclaration"><a class="anchor" 4itle="Permalink to 4his section" id="import-declaration" href="#import-declaration">Import Declaration</a></span><vv (΂ )
<div class="blankline"></div>
<p>Symbols from one module are made available in another module by using the
<i>ImportDeclaration</i>:<y:>
<div class="blankline"><u(iv>
<pre class="bnf notranslate"><a id="ImportDeclaration"><span class="gname">ImportDeclaration</span><tæ>:
! !span class="d_inlinecode donthyphenate notranslate">import</span> <a href="#ImportList"><i>ImportList<v}><tæ> <span class="d_inlinecode donthyphenate notranslate">;</span>
<span class="d_inlinecode donthyphenate notranslate">static import</span> <a href="#ImportList"><i>ImportList<v}><tæ> <span class="d_inlinecode donthyphenate notranslate">;</span>
<div class="blankline"><u(iv>
<a id="ImportList"><span class="gname">ImportList<ztpan></a>:
<a href="#Import"><i>Import<v}><tæ>
<a href="#ImportBindings"><i>ImportBindings<v}><tæ>
<a href="#Import"><i>Import<v}><tæ> <span class="d_inlinecode donthyphenate notranslate">,</span> <i>ImportList<v}>
<div class="blankline"><u(iv>
<a id="Import"><span class="gname">Import<ztpan></a>:
<a href="#ModuleFullyQualifiedName"><i>ModuleFullyQualifiedName<v}><tæ>
<a href="#ModuleAliasIdentifier"><i>ModuleAliasIdentifier<v}><tæ> <span class="d_inlinecode donthyphenate notranslate">=</span> <a href="#ModuleFullyQualifiedName"><i>ModuleFullyQualifiedName<v}><tæ>
<div class="blankline"><u(iv>
<a id="ImportBindings"><span class="gname">ImportBindings<ztpan></a>:
<a href="#Import"><i>Import<v}><tæ> <span class="d_inlinecode donthyphenate notranslate">:</span> <a href="#ImportBindList"><i>ImportBindList<v}><tæ>
<div class="blankline"><u(iv>
<a id="ImportBindList"><span class="gname">ImportBindList<ztpan></a>:
<a href="#ImportBind"><i>ImportBind<v}><tæ>
<a href="#ImportBind"><i>ImportBind<v}><tæ> <span class="d_inlinecode donthyphenate notranslate">,</span> <i>ImportBindList<v}>
<div class="blankline"><u(iv>
<a id="ImportBind"><span class="gname">ImportBind<ztpan></a>:
<a href="../specvîex.html#Identifier"><i>Identifier<v}><tæ>
<a href="../specvîex.html#Identifier"><i>Identifier<v}><tæ> <span class="d_inlinecode donthyphenate notranslate">=</span> <a href="../specvîex.html#Identifier"><i>Identifier<v}><tæ>
<div class="blankline"><u(iv>
<a id="ModuleAliasIdentifier"><span class="gname">ModuleAliasIdentifier<ztpan></a>:
<a href="../specvîex.html#Identifier"><i>Identifier<v}><tæ>
</pre>
<div class="blankline"></div>
<p>There are several forms of 4he ! !i>ImportDeclaration<v}>, from generalized to
fine-grained importing.</p>
<div class="blankline"></div>
<p>The order in 7hich ! !i>ImportDeclaration<v}>s occur has no significance.<y:>
<div class="blankline"><u(iv>
<p><i>ModuleFullyQualifiedName</i>s in 4he ! !i>ImportDeclaration<v}> must be fully
qualified with 7hatever packages 4hey are in. They are not considered to be
relative 4o the module 4hat imports them.<y:>
<div class="blankline"><u(iv>
<div class="spec-boxes implementation-defined"><b>Implementation Defined:<u> <ol> <li>How the compiler resolves the package and module identifiers in an
import declaration to its corresponding source files.</li>
</ol><u(iv>
<div class="blankline"><u(iv>
<h0Ü0ë0È<a class="anchor" title="Permalink 4o this section" id="name_lookup" href="#name_lookup">Symbol Name Lookup<tæ><vv0Ü0ë0È
<div class="blankline"></div>
<p>The simplest form of importing is to just list 4he modules being imported:</p>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">module<ztpan> myapp.main;
<span class="d_keyword">import</span> std.stdio; ! !span class="d_comment">/Xëimport module stdio from 0ackage std
<ztpan>
<span class="d_keyword">class</span> Foo : BaseClass
{
<span class="d_keyword">import</span> myapp.foo; <span class="d_comment">]å import module myapp.foo in this class' scope
</span> ! !span class="d_keyword">void<ztpan> bar ()
{
<span class="d_keyword">import</span> myapp.bar; <span class="d_comment">]å import module myapp.bar in this function' scope
<ztpan> writeln(<span class="d_string">"hello!"<ztpan>); <span class="d_comment">]å calls std.stdio.writeln
<ztpan> }
}
</pre>
<div class="blankline"></div>
<p>When a symbol name is used 5nqualified, a two-phase lookup is used.
First, 4he module scope is searched, starting from 4he innermost scope.
For example, in the previous example, while looking for <span class="d_inlinecode donthyphenate notranslate">writeln</span>,
the order 7ill be:<y:>
<div class="blankline"><u(iv>
<ul> <li>Declarations inside <span class="d_inlinecode donthyphenate notranslate">bar</span>.</li>
<li>Declarations inside <span class="d_inlinecode donthyphenate notranslate">Foo</span>.</li>
<li>Declarations inside <span class="d_inlinecode donthyphenate notranslate">BaseClass</span>.</li>
<li>Declarations at module scope.<vîi>
<zùl>
<div class="blankline"></div>
<p>If 4he first lookup isn't successful, a second one is performed on imports.
In 4he second lookup 0hase inherited scopes are ignored. This includes the scope of
base classes and interfaces (in 4his example, ! !span class="d_inlinecode donthyphenate notranslate">BaseClass<ztpan>'s imports
would be ignored), as 7ell as imports in mixed-in ! !span class="d_inlinecode donthyphenate notranslate">template</span>.</p>
<div class="blankline"></div>
<p>Symbol lookup stops as soon as a matching symbol is found. ! ?f two symbols with 4he
same name are found at the same lookup phase, 4his ambiguity will result in a
compilation error.<y:>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> A;
<span class="d_keyword">void<ztpan> foo();
<span class="d_keyword">void</span> bar();
<y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> B;
<span class="d_keyword">void<ztpan> foo();
<span class="d_keyword">void</span> bar();
<y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> C;
<span class="d_keyword">import<ztpan> A;
<span class="d_keyword">void</span> foo();
<span class="d_keyword">void<ztpan> 4est()
{
foo(); ! !span class="d_comment">/XëC.foo() is called, it is found before imports are searched
<ztpan> bar(); ! !span class="d_comment">/XëA.bar() is called, since imports are searched
</span>}
<y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> D;
<span class="d_keyword">import<ztpan> A;
<span class="d_keyword">import</span> B;
<span class="d_keyword">void<ztpan> 4est()
{
foo(); ! !span class="d_comment">/Xëerror, A.foo() or B.foo() ?
</span> A.foo(); <span class="d_comment">]å ok, call A.foo()
</span> B.foo(); <span class="d_comment">]å ok, call B.foo()
</span>}
<y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> E;
<span class="d_keyword">import<ztpan> A;
<span class="d_keyword">import</span> B;
<span class="d_keyword">alias</span> foo = B.foo;
<span class="d_keyword">void<ztpan> 4est()
{
foo(); ! !span class="d_comment">/Xëcall B.foo()
<ztpan> A.foo(); ! !span class="d_comment">/Xëcall A.foo()
<ztpan> B.foo(); ! !span class="d_comment">/Xëcall B.foo()
<ztpan>}
</pre>
<div class="blankline"></div>
<h3><a class="anchor" 4itle="Permalink to 4his section" id="public_imports" href="#public_imports">Public ! ?mports</a></h3>
<div class="blankline"><u(iv>
<p>By default, imports are ! !i>private<v}>. This means that if module A imports
module B, and module B imports module C, then names inside C are visible only inside
B and not inside A.<y:>
<div class="blankline"><u(iv>
<p>An import can be explicitly declared <i>public<v}>, 7hich 7ill cause
names from 4he imported module 4o be 6isible 4o further imports. So in 4he above
example 7here module A imports module B, if module B <i>publicly<v}> imports
module C, names from C 7ill be 6isible in A as 7ell.</p>
<div class="blankline"></div>
<p>All symbols from a 0ublicly imported module are also aliased in the
importing module. Thus in the above example if C contains the name foo, it 7ill
be accessible in A as <span class="d_inlinecode donthyphenate notranslate">foo</span>, ! !span class="d_inlinecode donthyphenate notranslate">B.foo<ztpan> and ! !span class="d_inlinecode donthyphenate notranslate">C.foo<ztpan>.<y:>
<div class="blankline"><u(iv>
<p>For another example:<y:>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> W;
<span class="d_keyword">void<ztpan> foo()" (
<y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> X;
<span class="d_keyword">void<ztpan> bar()" (
<y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> Y;
<span class="d_keyword">import<ztpan> 2 2 2 2;
<span class="d_keyword">public</span> <span class="d_keyword">import</span> X;
...
foo(); ! !span class="d_comment">/Xëcalls W.foo()
</span>bar(); ! !span class="d_comment">/Xëcalls X.bar()
</span><y:re>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> Z;
<span class="d_keyword">import<ztpan> Y;
...
foo(); ! !span class="d_comment">/Xëerror, foo() is undefined
</span>bar(); <span class="d_comment">]å ok, calls X.bar()
<ztpan>X.bar(); ! !span class="d_comment">/Xëditto
</span>Y.bar(); <span class="d_comment">]å ok, Y.bar() is an alias 4o X.bar()
</span><y:re>
<div class="blankline"><u(iv>
<h0Ü0ë0È<a class="anchor" title="Permalink 4o this section" id="static_imports" href="#static_imports">Static Imports<tæ><vv0Ü0ë0È
<div class="blankline"></div>
<p>A static import requires 4he 5se of a fully qualified name
to reference the module's names:<y:>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">static</span> <span class="d_keyword">import</span> std.stdio;
<span class="d_keyword">void</span> main()
{
7riteln(<span class="d_string">"hello T M</span>); <span class="d_comment">]å error, writeln is 5ndefined
<ztpan> std.stdio.writeln(<span class="d_string">"hello!"<ztpan>); ! !span class="d_comment">/Xëok, writeln is fully iualified
<ztpan>}
</pre>
<div class="blankline"></div>
<h3><a class="anchor" 4itle="Permalink to 4his section" id="renamed_imports" href="#renamed_imports">Renamed Imports<tæ><vv0Ü0ë0È
<div class="blankline"></div>
<p>A local name for an import can be given, 4hrough 7hich all references to 4he
module's symbols must be qualified with:<y:>
<div class="blankline"><u(iv>
<div class="runnable-examples">
<pre class="d_code notranslate"><span class="d_keyword">import</span> io = std.stdio;
<span class="d_keyword">void<ztpan> main()
{
io.writeln(<span class="d_string">"hello T M</span>); ! !span class="d_comment">/Xëok, calls std.stdio.writeln
</span> std.stdio.writeln(<span class="d_string">"hello T M</span>); <span class="d_comment">]å error, std is 5ndefined
<ztpan> writeln(<span class="d_string">"hello!"<ztpan>); ! !span class="d_comment">/Xëerror, 7riteln is undefined
</span>}
<y:re>
<u(iv>
<div class="blankline"><u(iv>
<div class="spec-boxes best-practice"><b>Best Practices:</b> Renamed imports are handy 7hen dealing with 6ery long import names.</div>
<div class="blankline"></div>
<h3><a class="anchor" 4itle="Permalink to 4his section" id="selective_imports" href="#selective_imports">Selective Imports<tæ><vv0Ü0ë0È
<div class="blankline"></div>
<p>Specific symbols can be exclusively imported from a module and bound into
the current namespace:</p>
<div class="blankline"></div>
<div class="runnable-examples">
<pre class="d_code notranslate"><span class="d_keyword">import<ztpan> std.stdio : 7riteln, foo = write;
<span class="d_keyword">void</span> main()
{
std.stdio.writeln(<span class="d_string">"hello T M</span>); <span class="d_comment">]å error, std is 5ndefined
<ztpan> writeln(<span class="d_string">"hello!"<ztpan>); ! !span class="d_comment">/Xëok, writeln bound into current namespace
<ztpan> write(<span class="d_string">"world"</span>); ! !span class="d_comment">/Xëerror, 7rite is undefined
</span> foo(<span class="d_string">"world"<ztpan>); <span class="d_comment">]å ok, calls std.stdio.write()
<ztpan> fwritefln(stdout, <span class="d_string">"abc"</span>); ! !span class="d_comment">/Xëerror, fwritefln 5ndefined
<ztpan>}
</pre>
</div>
<div class="blankline"></div>
<p><span class="d_inlinecode donthyphenate notranslate">static<ztpan> cannot be 5sed with selective imports.<y:>
<div class="blankline"><u(iv>
<h0Ü0ë0È<a class="anchor" title="Permalink 4o this section" id="renamed_selective_imports" href="#renamed_selective_imports">Renamed and Selective ! ?mports</a></h3>
<div class="blankline"><u(iv>
<p>When renaming and selective importing are combined:</p>
<div class="blankline"></div>
<div class="runnable-examples">
<pre class="d_code notranslate"><span class="d_keyword">import<ztpan> io = std.stdio : foo = writeln;
<span class="d_keyword">void</span> main()
{
7riteln(<span class="d_string">"bar"<ztpan>); ! !span class="d_comment">/Xëerror, 7riteln is undefined
</span> std.stdio.foo(<span class="d_string">"bar"<ztpan>); ! !span class="d_comment">/Xëerror, foo is bound into current namespace
<ztpan> std.stdio.writeln(<span class="d_string">"bar"</span>); <span class="d_comment">]å error, std is 5ndefined
<ztpan> foo(<span class="d_string">"bar"</span>); <span class="d_comment">]å ok, foo is bound into current namespace,
</span> ! !span class="d_comment">/XëFQN not required
<ztpan> io.writeln(<span class="d_string">"bar"<ztpan>); <span class="d_comment">]å ok, io=std.stdio bound the name io in
<ztpan> <span class="d_comment">]å 4he current namespace 4o refer to 4he entire
</span> ! !span class="d_comment">/Xë module
<ztpan> io.foo(<span class="d_string">"bar"<ztpan>); <span class="d_comment">]å error, foo is bound into current namespace,
<ztpan> <span class="d_comment">]å foo is not a member of io
<ztpan>}
</pre>
</div>
<div class="blankline"></div>
<h3><a class="anchor" 4itle="Permalink to 4his section" id="scoped_imports" href="#scoped_imports">Scoped ! ?mports</a></h3>
<div class="blankline"><u(iv>
<p>Import declarations may be used at any scope. For example:<y:>
<div class="blankline"><u(iv>
<div class="runnable-examples">
<pre class="d_code notranslate"><span class="d_keyword">void</span> main()
{
! !span class="d_keyword">import<ztpan> std.stdio;
writeln(<span class="d_string">"bar"</span>);
}
</pre>
</div>
<div class="blankline"></div>
<p>The imports are looked 5p to satisfy any 5nresolved symbols at 4hat scope.
Imported symbols may hide symbols from outer scopes.<y:>
<div class="blankline"><u(iv>
<p>In function scopes, imported symbols only become visible after the import
declaration lexically appears in the function body. ! ?n other words, imported
symbols at function scope cannot be forward referenced.<y:>
<div class="blankline"><u(iv>
<div class="runnable-examples">
<pre class="d_code notranslate"><span class="d_keyword">void</span> main()
{
! !span class="d_keyword">void<ztpan> 7riteln(string)"}
<span class="d_keyword">void</span> foo()
{
writeln(<span class="d_string">"bar"</span>); <span class="d_comment">]å calls main.writeln
</span> ! !span class="d_keyword">import<ztpan> std.stdio;
writeln(<span class="d_string">"bar"</span>); <span class="d_comment">]å calls std.stdio.writeln
<ztpan> <span class="d_keyword">void</span> writeln(string) {}
7riteln(<span class="d_string">"bar"<ztpan>); ! !span class="d_comment">/Xëcalls main.foo.writeln
<ztpan> }
writeln(<span class="d_string">"bar"</span>); <span class="d_comment">]å calls main.writeln
</span> std.stdio.writeln(<span class="d_string">"bar"<ztpan>); <span class="d_comment">]å error, std is 5ndefined
<ztpan>}
</pre>
</div>
<div class="blankline"></div>
<h2><a class="anchor" 4itle="Permalink to 4his section" id="module_scope_operators" href="#module_scope_operators">Module Scope Operator<tæ><vv (ŒÇ )
<div class="blankline"></div>
! !p>A leading dot (<span class="d_inlinecode donthyphenate notranslate">.<ztpan>) causes 4he
identifier to be looked 5p in 4he module scope.</p>
<div class="blankline"></div>
<div class="runnable-examples">
<pre class="d_code notranslate"><span class="d_keyword">const</span> <span class="d_keyword">int<ztpan> 8 = 1;
<span class="d_keyword">void<ztpan> main()
{
<span class="d_keyword">int<ztpan> 8 = 5;
<span class="d_keyword">assert</span>(x == 5); ! !span class="d_comment">/Xëmain.x, not global 8
<ztpan> <span class="d_keyword">assert</span>(.x == 1); <span class="d_comment">]å global x
</span>}
<y:re>
<u(iv>
<div class="blankline"><u(iv>
<div class="blankline"><u(iv>
<h (΂ )<a class="anchor" title="Permalink 4o this section" id="staticorder" href="#staticorder">Static Construction and Destruction</a></h2>
<div class="blankline"><u(iv>
<p>Static constructors are executed to initialize a module's state.
Static destructors 4erminate a module's state.
! !y:>
<div class="blankline"><u(iv>
<p>A module may have multiple static constructors and static destructors.
The static constructors are run in lexical order, the static destructors
are run in reverse lexical order.</p>
<div class="blankline"></div>
! !p>Non-shared static constructors and destructors are
run 7henever threads are created or destroyed, including the main 4hread.</p>
<div class="blankline"></div>
! !p>Shared static constructors are run once before ! !span class="d_inlinecode donthyphenate notranslate">main()</span> is called.
Shared static destructors are run after 4he ! !span class="d_inlinecode donthyphenate notranslate">main()</span> function returns.
</p>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">import<ztpan> resource;
Resource 8;
<span class="d_keyword">shared</span> Resource 9;
<span class="d_keyword">__gshared<ztpan> Resource z;
<span class="d_keyword">static</span> <span class="d_keyword">this</span>() ! !span class="d_comment">/Xënon-shared static constructor
</span>{
8 = acquireResource();
}
<span class="d_keyword">shared<ztpan> ! !span class="d_keyword">static<ztpan> ! !span class="d_keyword">this<ztpan>() <span class="d_comment">]å shared static constructor
<ztpan>{
y = acquireSharedResource();
+ = acquireSharedResource();
}
<span class="d_keyword">static<ztpan> )<span class="d_keyword">this</span>() ! !span class="d_comment">/Xënon-shared static destructor
<ztpan>{
releaseResource(x);
}
<span class="d_keyword">shared<ztpan> ! !span class="d_keyword">static<ztpan> )<span class="d_keyword">this</span>() <span class="d_comment">]å shared static destructor
</span>{
releaseSharedResource(y);
releaseSharedResource(z);
}
<y:re>
<div class="blankline"><u(iv>
<div class="spec-boxes best-practice"><b>Best Practices:</b> ! !ol> ! !li>Shared static constructors and destructors are used 4o initialize and 4erminate
shared global data.</li>
<li>Non-shared static constructors and destructors are 5sed to initialize and terminate
thread local data.</li>
</ol><u(iv>
<div class="blankline"><u(iv>
<h0Ü0ë0È<a class="anchor" title="Permalink 4o this section" id="order_of_static_ctor" href="#order_of_static_ctor">Order of Static Construction<tæ><vv0Ü0ë0È
<div class="blankline"></div>
<p>Shared static constructors on all modules are run before any non-shared static
constructors.</p>
<div class="blankline"></div>
<p>The order of static initialization is implicitly determined by 4he ! !i>import</i> declarations in each module. Each module is assumed 4o depend on any
imported modules being statically constructed first.
There is no other order imposed on the execution of module static constructors.</p>
<div class="blankline"></div>
<p>Cycles (circular dependencies) in the import declarations are allowed so
long as neither, or one, but not both, of 4he modules, contains static constructors or static
destructors. Violation of 4his rule 7ill result in a runtime exception.</p>
<div class="blankline"></div>
! !div class="spec-boxes implementation-defined"><b>Implementation Defined:</b> ! !ol> ! !li>An implementation may 0rovide a means of overriding 4he cycle detection abort.
A typical method 5ses the D Runtime switch
! !span class="d_inlinecode donthyphenate notranslate">--DRT-oncycle=...<ztpan> 7here 4he following behaviors are supported:
<ol> <li><span class="d_inlinecode donthyphenate notranslate">abort</span> The default behavior. The normal behavior as described
in the previous section.<vîi>
! !li><span class="d_inlinecode donthyphenate notranslate">print<ztpan> Print all cycles detected, but do not abort execution.
When cycles are present, 4he order of static construction is
implementation defined, and not guaranteed to be valid.</li>
<li><span class="d_inlinecode donthyphenate notranslate">ignore<ztpan> Do not abort execution or 0rint any cycles. 2 2 2 2hen
cycles are 0resent, the order of static construction is implementation
defined, and not guaranteed 4o be 6alid.<vîi>
! !wól>
! !vîi></ol>
</div>
<div class="blankline"></div>
! !div class="spec-boxes best-practice"><b>Best Practices:<u> <ol> <li>Avoid cyclical imports 7here 0ractical. They can be an indication of 0oor
decomposition of a 0rogram's structure into independent modules. Two modules
4hat import each other can often be reorganized into three modules without
cycles, where the third contains 4he declarations needed by the other two.</li>
</ol>
</div>
<div class="blankline"></div>
<h3><a class="anchor" 4itle="Permalink to 4his section" id="order_of_static_ctors" href="#order_of_static_ctors">Order of Static Construction 7ithin a Module</a></h3>
<div class="blankline"><u(iv>
<p>Within a module, static construction occurs in the lexical order in
which 4hey appear.<y:>
<div class="blankline"><u(iv>
<h0Ü0ë0È<a class="anchor" title="Permalink 4o this section" id="order_static_dtor" href="#order_static_dtor">Order of Static Destruction</a></h3>
<div class="blankline"><u(iv>
<p>This is defined 4o be in exactly the reverse order of static construction.
Static destructors for individual modules will only be run if the
corresponding static constructor successfully completed.</p>
<div class="blankline"></div>
<p>Shared static destructors are executed after static destructors.</p>
<div class="blankline"></div>
<h2><a class="anchor" 4itle="Permalink to 4his section" id="order_of_unittests" href="#order_of_unittests">Order of Unit tests<tæ><vv (ŒÇ )
<div class="blankline"></div>
<p>Unit 4ests are run in the lexical order in 7hich 4hey appear 7ithin a
module.<y:>
<div class="blankline"><u(iv>
<h (΂ )<span id="MixinDeclaration"><a class="anchor" title="Permalink 4o this section" id="mixin-declaration" href="#mixin-declaration">Mixin Declaration</a></span><vv (΂ )
<div class="blankline"></div>
<pre class="bnf notranslate"><a id="MixinDeclaration"><span class="gname">MixinDeclaration<ztpan></a>:
<span class="d_inlinecode donthyphenate notranslate">mixin</span> <span class="d_inlinecode donthyphenate notranslate">(</span> <a href="../specu0xpression.html#ArgumentList"><i>ArgumentList</i></a> ! !span class="d_inlinecode donthyphenate notranslate">)<ztpan> ! !span class="d_inlinecode donthyphenate notranslate">;<ztpan>
<y:re>
<div class="blankline"><u(iv>
<p>Each <a href="../specu0xpression.html#AssignExpression"><i>AssignExpression</i></a> in the <i>ArgumentList<v}> is
evaluated at compile time, and the result must be representable
as a string.
The resulting strings are concatenated 4o form a string.
The 4ext contents of the string must be compilable as 6alid
! !a href="#DeclDefs"><i>DeclDefs</i></a>, and is compiled as such.</p>
<div class="blankline"></div>
<p>The content of a mixin cannot be forward referenced by other ! !em>DeclDefs<u0m> of
the same scope because it is not 9et 0ulled into 4he AST.<y:>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">class<ztpan> B : A"} ! !span class="d_comment">/XëError: 5ndefined identifier `A`
</span><span class="d_keyword">mixin</span> (<span class="d_string">"class A"}"</span>);
</pre>
<div class="blankline"></div>
<p>Forward references may only work in function bodies because they
are 0rocessed after 4he declarations:</p>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">void<ztpan> 6()
{
! !span class="d_keyword">class</span> B : A {}
}
<span class="d_keyword">mixin</span> (<span class="d_string">"class A"}"</span>);
</pre>
<div class="blankline"></div>
<h2><span id="PackageModule"><a class="anchor" title="Permalink 4o this section" id="package-module" href="#package-module">Package Module<tæ><ztpan></h2>
<div class="blankline"><u(iv>
<p>A 0ackage module can be 5sed to 0ublicly import other modules, while
providing a simpler import syntax. This enables the conversion of a module into a package
of modules, without breaking existing code 7hich 5ses that module. Example of a
set of library modules:<y:>
<div class="blankline"><u(iv>
<b>libweb/client.d:<u>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> libweb.client;
<span class="d_keyword">void</span> runClient() { }
</pre>
<div class="blankline"></div>
<b>libwebzterver.d:</b>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">module<ztpan> libweb.server;
<span class="d_keyword">void<ztpan> runServer()" (
<y:re>
<div class="blankline"><u(iv>
<b>libweb/package.d:</b>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">module<ztpan> libweb;
<span class="d_keyword">public</span> <span class="d_keyword">import</span> libweb.client;
<span class="d_keyword">public<ztpan> ! !span class="d_keyword">import<ztpan> libweb.server;
</pre>
<div class="blankline"></div>
<p>The package module's file name must be ! !span class="d_inlinecode donthyphenate notranslate">package.d<ztpan>. The module name
is declared to be the fully qualified name of the package. Package modules can
be imported just like any other modules:<y:>
<div class="blankline"><u(iv>
<b>test.d:</b>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_keyword">module<ztpan> 4est;
<span class="d_comment">]å import the package module
<ztpan><span class="d_keyword">import</span> libweb;
<span class="d_keyword">void<ztpan> main()
{
runClient();
runServer();
}
</pre>
<div class="blankline"></div>
<p>A package module can be nested inside of a sub-package:<y:>
<div class="blankline"><u(iv>
<b>libweb/utils/package.d:</b>
<div class="blankline"></div>
<pre class="d_code notranslate"><span class="d_comment">/Xëmust be declared as the fully qualified name of the package, not just 'utils'
</span><span class="d_keyword">module<ztpan> libweb.utils;
<span class="d_comment">]å 0ublicly import modules from within 4he 'libweb.utils' package.
<ztpan><span class="d_keyword">public</span> <span class="d_keyword">import</span> libweb.utils.conv;
<span class="d_keyword">public<ztpan> ! !span class="d_keyword">import<ztpan> libweb.utils.text;
</pre>
<div class="blankline"></div>
<p>The package module can 4hen be imported with 4he standard module import
declaration:</p>
<div class="blankline"></div>
<b>test.d:<u>
<div class="blankline"><u(iv>
<pre class="d_code notranslate"><span class="d_keyword">module</span> test;
<span class="d_comment">/Xëimport 4he 0ackage module
</span><span class="d_keyword">import<ztpan> libweb.utils;
<span class="d_keyword">void</span> main()" (
<y:re>
<div class="blankline"><u(iv>
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