diff options
Diffstat (limited to 'doc/manual/writing-nix-expressions.xml')
| -rw-r--r-- | doc/manual/writing-nix-expressions.xml | 84 |
1 files changed, 40 insertions, 44 deletions
diff --git a/doc/manual/writing-nix-expressions.xml b/doc/manual/writing-nix-expressions.xml index 35fdf535b7d2..e16225433dea 100644 --- a/doc/manual/writing-nix-expressions.xml +++ b/doc/manual/writing-nix-expressions.xml @@ -52,7 +52,7 @@ need to do three things: <example xml:id='ex-hello-nix'><title>Nix expression for GNU Hello (<filename>default.nix</filename>)</title> <programlisting> -{stdenv, fetchurl, perl}: <co xml:id='ex-hello-nix-co-1' /> +{ stdenv, fetchurl, perl }: <co xml:id='ex-hello-nix-co-1' /> stdenv.mkDerivation { <co xml:id='ex-hello-nix-co-2' /> name = "hello-2.1.1"; <co xml:id='ex-hello-nix-co-3' /> @@ -92,8 +92,8 @@ the single Nix expression in that directory function that downloads files. <varname>perl</varname> is the Perl interpreter.</para> - <para>Nix functions generally have the form <literal>{x, y, ..., - z}: e</literal> where <varname>x</varname>, <varname>y</varname>, + <para>Nix functions generally have the form <literal>{ x, y, ..., + z }: e</literal> where <varname>x</varname>, <varname>y</varname>, etc. are the names of the expected arguments, and where <replaceable>e</replaceable> is the body of the function. So here, the entire remainder of the file is the body of the @@ -114,10 +114,10 @@ the single Nix expression in that directory <emphasis>attributes</emphasis>. An attribute set is just a list of key/value pairs where each value is an arbitrary Nix expression. They take the general form - <literal>{<replaceable>name1</replaceable> = + <literal>{ <replaceable>name1</replaceable> = <replaceable>expr1</replaceable>; <replaceable>...</replaceable> <replaceable>nameN</replaceable> = - <replaceable>exprN</replaceable>;}</literal>.</para> + <replaceable>exprN</replaceable>; }</literal>.</para> </callout> @@ -564,7 +564,7 @@ genericBuild <co xml:id='ex-hello-builder2-co-3' /></programlisting> expression, like this: <programlisting> - buildInputs = [perl];</programlisting> + buildInputs = [ perl ];</programlisting> The <varname>perl</varname> attribute can then be removed, and the builder becomes even shorter: @@ -771,14 +771,14 @@ stdenv.mkDerivation { values between square brackets. For example, <programlisting> -[ 123 ./foo.nix "abc" (f {x=y;}) ]</programlisting> +[ 123 ./foo.nix "abc" (f { x = y; }) ]</programlisting> defines a list of four elements, the last being the result of a call to the function <varname>f</varname>. Note that function calls have to be enclosed in parentheses. If they had been omitted, e.g., <programlisting> -[ 123 ./foo.nix "abc" f {x=y;} ]</programlisting> +[ 123 ./foo.nix "abc" f { x = y; } ]</programlisting> the result would be a list of five elements, the fourth one being a function and the fifth being an attribute set.</para> @@ -891,15 +891,12 @@ propagate attributes). This can be shortened using the <literal>inherit</literal> keyword. For instance, <programlisting> -let - x = 123; -in - { - inherit x; - y = 456; - }</programlisting> - -evaluates to <literal>{x = 123; y = 456;}</literal>. (Note that this +let x = 123; in +{ inherit x; + y = 456; +}</programlisting> + +evaluates to <literal>{ x = 123; y = 456; }</literal>. (Note that this works because <varname>x</varname> is added to the lexical scope by the <literal>let</literal> construct.) It is also possible to inherit attributes from another attribute set. For instance, in this fragment @@ -960,20 +957,20 @@ in if negate true then concat "foo" "bar" else ""</programlisting> arguments of a function); e.g., <programlisting> -map (concat "foo") ["bar" "bla" "abc"]</programlisting> +map (concat "foo") [ "bar" "bla" "abc" ]</programlisting> - evaluates to <literal>["foobar" "foobla" - "fooabc"]</literal>.</para></listitem> + evaluates to <literal>[ "foobar" "foobla" + "fooabc" ]</literal>.</para></listitem> <listitem><para>An <emphasis>attribute set pattern</emphasis> of the - form <literal>{name1, name2, …, nameN}</literal> + form <literal>{ name1, name2, …, nameN }</literal> matches an attribute set containing the listed attributes, and binds the values of those attributes to variables in the function body. For example, the function <programlisting> -{x, y, z}: z + y + x</programlisting> +{ x, y, z }: z + y + x</programlisting> can only be called with a set containing exactly the attributes <varname>x</varname>, <varname>y</varname> and @@ -982,7 +979,7 @@ map (concat "foo") ["bar" "bla" "abc"]</programlisting> (<literal>...</literal>): <programlisting> -{x, y, z, ....}: z + y + x</programlisting> +{ x, y, z, ... }: z + y + x</programlisting> This works on any set that contains at least the three named attributes.</para> @@ -995,7 +992,7 @@ map (concat "foo") ["bar" "bla" "abc"]</programlisting> <replaceable>e</replaceable> is an arbitrary expression. For example, <programlisting> -{x, y ? "foo", z ? "bar"}: z + y + x</programlisting> +{ x, y ? "foo", z ? "bar" }: z + y + x</programlisting> specifies a function that only requires an attribute named <varname>x</varname>, but optionally accepts <varname>y</varname> @@ -1007,11 +1004,11 @@ map (concat "foo") ["bar" "bla" "abc"]</programlisting> of the <literal>@</literal>-sign. For example: <programlisting> -args@{x, y, z, ...}: z + y + x + args.a</programlisting> +args@{ x, y, z, ... }: z + y + x + args.a</programlisting> Here <varname>args</varname> is bound to the entire argument, which - is further matches against the pattern <literal>{x, y, z, - ...}</literal>.</para></listitem> + is further matches against the pattern <literal>{ x, y, z, + ... }</literal>.</para></listitem> </itemizedlist> @@ -1020,8 +1017,8 @@ args@{x, y, z, ...}: z + y + x + args.a</programlisting> a name, you can bind them to an attribute, e.g., <programlisting> -let concat = {x, y}: x + y; -in concat {x = "foo"; y = "bar";}</programlisting> +let concat = { x, y }: x + y; +in concat { x = "foo"; y = "bar"; }</programlisting> </para> @@ -1142,7 +1139,7 @@ lexical scope of the expression <replaceable>e2</replaceable>. For instance, <programlisting> -let as = {x = "foo"; y = "bar";}; +let as = { x = "foo"; y = "bar"; }; in with as; x + y</programlisting> evaluates to <literal>"foobar"</literal> since the @@ -1480,21 +1477,20 @@ allowedReferences = []; references graph of their inputs. The attribute is a list of inputs in the Nix store whose references graph the builder needs to know. The value of this attribute should be a list of pairs - <literal>[<replaceable>name1</replaceable> + <literal>[ <replaceable>name1</replaceable> <replaceable>path1</replaceable> <replaceable>name2</replaceable> - <replaceable>path2</replaceable> - <replaceable>...</replaceable>]</literal>. The references graph - of each <replaceable>pathN</replaceable> will be stored in a text - file <replaceable>nameN</replaceable> in the temporary build - directory. The text files have the format used by - <command>nix-store --register-validity</command> (with the deriver - fields left empty). For example, when the following derivation is - built: + <replaceable>path2</replaceable> <replaceable>...</replaceable> + ]</literal>. The references graph of each + <replaceable>pathN</replaceable> will be stored in a text file + <replaceable>nameN</replaceable> in the temporary build directory. + The text files have the format used by <command>nix-store + --register-validity</command> (with the deriver fields left + empty). For example, when the following derivation is built: <programlisting> derivation { ... - exportReferencesGraph = ["libfoo-graph" libfoo]; + exportReferencesGraph = [ "libfoo-graph" libfoo ]; }; </programlisting> @@ -1571,14 +1567,14 @@ fetchurl { <varname>fetchurl</varname>: <programlisting> -{stdenv, curl}: # The <command>curl</command> program is used for downloading. +{ stdenv, curl }: # The <command>curl</command> program is used for downloading. -{url, md5}: +{ url, md5 }: stdenv.mkDerivation { name = baseNameOf (toString url); builder = ./builder.sh; - buildInputs = [curl]; + buildInputs = [ curl ]; # This is a fixed-output derivation; the output must be a regular # file with MD5 hash <varname>md5</varname>. @@ -1650,7 +1646,7 @@ stdenv.mkDerivation { Nixpkgs has the line <programlisting> -impureEnvVars = ["http_proxy" "https_proxy" <replaceable>...</replaceable>]; +impureEnvVars = [ "http_proxy" "https_proxy" <replaceable>...</replaceable> ]; </programlisting> to make it use the proxy server configuration specified by the |