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rewrite the section about imports

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Rob Pike 2009-09-25 17:00:22 -07:00
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@ -4176,23 +4176,12 @@ An implementation may require that all source files for a package inhabit the sa
<h3 id="Import_declarations">Import declarations</h3>
<p>
An import declaration states that the current package depends on the
<i>imported</i> package and provides acccess to its
<a href="#Exported_identifiers">exported identifiers</a>.
</p>
<p>
The import declaration binds a package name to the imported package (except in
the case of <code>.</code> or <code>_</code> imports; see below). The package name
denotes the imported package within the current source file. If no explicit
package name is present, the package name defined within the source
files of the imported package is used.
</p>
<p>
The imported package is specified by an import path; the meaning of the path
is implementation-dependent. It may be a file name relative to a repository
of installed packages and the file a (compiled) implementation of the package.
An import declaration states that the source file containing the
declaration uses identifiers
<a href="#Exported_identifiers">exported</a> by the <i>imported</i>
package and enables access to them. The import names an
identifier (PackageName) to be used for access and an ImportPath
that specifies the package to be imported.
</p>
<pre class="ebnf">
@ -4203,22 +4192,30 @@ ImportPath = StringLit .
</pre>
<p>
If a package <code>A</code> is imported by a package <code>P</code> and
<code>A</code> exports an identifier <code>X</code>, then <code>X</code>
may be referred to by the <a href="#Qualified_identifiers">qualified identifier</a>
<code>A.X</code> within <code>P</code>. If an explicit package name
<code>B</code> is present, <code>X</code> must be referred to as <code>B.X</code>.
Finally, if the import declaration uses an explicit period
(<code>.</code>) for the package name, <code>X</code> will be declared
in the current file's <a href="#Blocks">file block</a> and can be accessed
without a qualifier.
The PackageName is used in <a href="#Qualified_identifiers">qualified identifiers</a>
to access the exported identifiers of the package within the importing source file.
It is declared in the <a href="#Blocks">file block</a>.
If the PackageName is omitted, it defaults to the identifier specified in the
<a href="#Package_clauses">package clause</a> of the imported package.
If an explicit period (<code>.</code>) appears instead of a name, all the
package's exported identifiers will be declared in the current file's
file block and can be accessed without a qualifier.
</p>
<p>
In this table, assume we have compiled a package named
<code>math</code>, which exports function <code>Sin</code>, and
installed the compiled package in file
The interpretation of the ImportPath is implementation-dependent but
it is typically a substring of the full file name of the compiled
package and may be relative to a repository of installed packages.
</p>
<p>
Assume we have compiled a package containing the package clause
<code>package math</code>, which exports function <code>Sin</code>, and
installed the compiled package in the file identified by
<code>"lib/math"</code>.
This table illustrates how <code>Sin</code> may be accessed in files
that import the package after the
various types of import declaration.
</p>
<pre class="grammar">
@ -4230,6 +4227,8 @@ import . "lib/math" Sin
</pre>
<p>
An import declaration declares a dependency relation between
the importing and imported package.
It is illegal for a package to import itself or to import a package without
referring to any of its exported identifiers. To import a package solely for
its side-effects (initialization), use the <a href="#Blank_identifier">blank</a>