277 lines
No EOL
8.1 KiB
XML
277 lines
No EOL
8.1 KiB
XML
<chapter>
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<title>Nix Language Reference</title>
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<sect1>
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<title>Grammar</title>
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<productionset>
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<title>Expressions</title>
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<production id="nix.expr">
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<lhs>Expr</lhs>
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<rhs>
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<nonterminal def="#nix.expr_function" />
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</rhs>
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</production>
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<production id="nix.expr_function">
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<lhs>ExprFunction</lhs>
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<rhs>
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'{' <nonterminal def="#nix.formals" /> '}' ':' <nonterminal def="#nix.expr_function" />
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<sbr />|
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<nonterminal def="#nix.expr_assert" />
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</rhs>
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</production>
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<production id="nix.expr_assert">
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<lhs>ExprAssert</lhs>
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<rhs>
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'assert' <nonterminal def="#nix.expr" /> ';' <nonterminal def="#nix.expr_assert" />
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<sbr />|
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<nonterminal def="#nix.expr_if" />
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</rhs>
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</production>
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<production id="nix.expr_if">
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<lhs>ExprIf</lhs>
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<rhs>
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'if' <nonterminal def="#nix.expr" /> 'then' <nonterminal def="#nix.expr" />
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'else' <nonterminal def="#nix.expr" />
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<sbr />|
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<nonterminal def="#nix.expr_op" />
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</rhs>
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</production>
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<production id="nix.expr_op">
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<lhs>ExprOp</lhs>
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<rhs>
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'!' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '==' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '!=' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '&&' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '||' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '->' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '//' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '~' <nonterminal def="#nix.expr_op" />
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<sbr />|
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<nonterminal def="#nix.expr_op" /> '?' <nonterminal def="#nix.id" />
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<sbr />|
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<nonterminal def="#nix.expr_app" />
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</rhs>
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</production>
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<production id="nix.expr_app">
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<lhs>ExprApp</lhs>
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<rhs>
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<nonterminal def="#nix.expr_app" /> '.' <nonterminal def="#nix.expr_select" />
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<sbr />|
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<nonterminal def="#nix.expr_select" />
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</rhs>
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</production>
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<production id="nix.expr_select">
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<lhs>ExprSelect</lhs>
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<rhs>
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<nonterminal def="#nix.expr_select" /> <nonterminal def="#nix.id" />
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<sbr />|
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<nonterminal def="#nix.expr_simple" />
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</rhs>
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</production>
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<production id="nix.expr_simple">
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<lhs>ExprSimple</lhs>
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<rhs>
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<nonterminal def="#nix.id" /> |
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<nonterminal def="#nix.int" /> |
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<nonterminal def="#nix.str" /> |
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<nonterminal def="#nix.path" /> |
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<nonterminal def="#nix.uri" />
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<sbr />|
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'true' | 'false' | 'null'
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<sbr />|
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'(' <nonterminal def="#nix.expr" /> ')'
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<sbr />|
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'{' <nonterminal def="#nix.bind" />* '}'
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<sbr />|
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'let' '{' <nonterminal def="#nix.bind" />* '}'
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<sbr />|
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'rec' '{' <nonterminal def="#nix.bind" />* '}'
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<sbr />|
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'[' <nonterminal def="#nix.expr_select" />* ']'
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</rhs>
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</production>
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<production id="nix.bind">
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<lhs>Bind</lhs>
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<rhs>
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<nonterminal def="#nix.id" /> '=' <nonterminal def="#nix.expr" /> ';'
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<sbr />|
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'inherit' ('(' <nonterminal def="#nix.expr" /> ')')? <nonterminal def="#nix.id" />* ';'
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</rhs>
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</production>
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<production id="nix.formals">
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<lhs>Formals</lhs>
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<rhs>
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<nonterminal def="#nix.formal" /> ',' <nonterminal def="#nix.formals" />
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| <nonterminal def="#nix.formal" />
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</rhs>
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</production>
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<production id="nix.formal">
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<lhs>Formal</lhs>
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<rhs>
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<nonterminal def="#nix.id" />
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<sbr />|
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<nonterminal def="#nix.id" /> '?' <nonterminal def="#nix.expr" />
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</rhs>
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</production>
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</productionset>
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<productionset>
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<title>Terminals</title>
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<production id="nix.id">
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<lhs>Id</lhs>
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<rhs>[a-zA-Z\_][a-zA-Z0-9\_\']*</rhs>
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</production>
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<production id="nix.int">
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<lhs>Int</lhs>
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<rhs>[0-9]+</rhs>
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</production>
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<production id="nix.str">
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<lhs>Str</lhs>
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<rhs>\"[^\n\"]*\"</rhs>
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</production>
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<production id="nix.path">
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<lhs>Path</lhs>
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<rhs>[a-zA-Z0-9\.\_\-\+]*(\/[a-zA-Z0-9\.\_\-\+]+)+</rhs>
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</production>
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<production id="nix.uri">
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<lhs>Uri</lhs>
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<rhs>[a-zA-Z][a-zA-Z0-9\+\-\.]*\:[a-zA-Z0-9\%\/\?\:\@\&\=\+\$\,\-\_\.\!\~\*\']+</rhs>
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</production>
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<production id="nix.ws">
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<lhs>Whitespace</lhs>
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<rhs>
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[ \t\n]+
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<sbr />|
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\#[^\n]*
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<sbr />|
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\/\*(.|\n)*\*\/
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</rhs>
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</production>
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</productionset>
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</sect1>
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<sect1>
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<title>Semantics</title>
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<sect2>
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<title>Built-in functions</title>
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<para>
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The Nix language provides the following built-in function
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(<quote>primops</quote>):
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</para>
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<variablelist>
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<varlistentry>
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<term><function>import</function>
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<replaceable>e</replaceable></term>
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<listitem>
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<para>
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Evaluates the expression <replaceable>e</replaceable>,
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which must yield a path value. The Nix expression
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stored at this path in the file system is then read,
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parsed, and evaluated. Returns the result of the
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evaluation of the Nix expression just read.
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</para>
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<para>
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Example: <literal>import ./foo.nix</literal> evaluates
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the expression stored in <filename>foo.nix</filename>
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(in the directory containing the expression in which the
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<function>import</function> occurs).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><function>derivation</function>
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<replaceable>e</replaceable></term>
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<listitem>
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<para>
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Evaluates the expression <replaceable>e</replaceable>,
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which must yield an attribute set. [...]
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><function>baseNameOf</function>
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<replaceable>e</replaceable></term>
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<listitem>
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<para>
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Evaluates the expression <replaceable>e</replaceable>,
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which must yield a string value, and returns a string
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representing its <emphasis>base name</emphasis>. This
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is the substring following the last path separator
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(<literal>/</literal>).
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</para>
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<para>
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Example: <literal>baseNameOf "/foo/bar"</literal>
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returns <literal>"bar"</literal>, and
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<literal>baseNameOf "/foo/bar/"</literal> returns
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<literal>""</literal>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><function>toString</function>
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<replaceable>e</replaceable></term>
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<listitem>
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<para>
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Evaluates the expression <replaceable>e</replaceable>
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and coerces it into a string, if possible. Only
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strings, paths, and URIs can be so coerced.
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</para>
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<para>
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Example: <literal>toString
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http://www.cs.uu.nl/</literal> returns
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<literal>"http://www.cs.uu.nl/"</literal>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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</sect1>
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</chapter> |