* New built-in function `builtins.attrNames' that returns the

names of the attributes in an attribute set.
This commit is contained in:
Eelco Dolstra 2006-12-12 16:14:31 +00:00
parent 5e6699188f
commit 1a7e88bbd9
4 changed files with 51 additions and 0 deletions

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@ -1362,6 +1362,24 @@ is also available as <function>builtins.derivation</function>.</para>
</varlistentry>
<varlistentry><term><function>builtins.attrNames</function>
<replaceable>attrs</replaceable></term>
<listitem><para>Return the names of the attributes in the
attribute set <replaceable>attrs</replaceable> in a sorted list.
For instance, <literal>builtins.attrNames {y = 1; x =
"foo";}</literal> evaluates to <literal>["x" "y"]</literal>.
There is no built-in function <function>attrValues</function>, but
you can easily define it yourself:
<programlisting>
attrValues = attrs: map (name: builtins.getAttr name attrs) (builtins.attrNames attrs);</programlisting>
</para></listitem>
</varlistentry>
<varlistentry><term><function>baseNameOf</function> <replaceable>s</replaceable></term>
<listitem><para>Return the <emphasis>base name</emphasis> of the

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@ -620,6 +620,26 @@ static Expr primGetEnv(EvalState & state, const ATermVector & args)
}
/* Return the names of the attributes in an attribute set as a sorted
list of strings. */
static Expr primAttrNames(EvalState & state, const ATermVector & args)
{
ATermMap attrs(128); /* !!! */
queryAllAttrs(evalExpr(state, args[0]), attrs);
StringSet names;
for (ATermMap::const_iterator i = attrs.begin(); i != attrs.end(); ++i)
names.insert(aterm2String(i->key));
ATermList list = ATempty;
for (StringSet::const_reverse_iterator i = names.rbegin();
i != names.rend(); ++i)
list = ATinsert(list, makeStr(*i, PathSet()));
return makeList(list);
}
/* Apply a function to every element of a list. */
static Expr primMap(EvalState & state, const ATermVector & args)
{
@ -732,6 +752,7 @@ void EvalState::addPrimOps()
addPrimOp("__head", 1, primHead);
addPrimOp("__tail", 1, primTail);
addPrimOp("__getEnv", 1, primGetEnv);
addPrimOp("__attrNames", 1, primAttrNames);
addPrimOp("map", 2, primMap);
addPrimOp("__getAttr", 2, primGetAttr);

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@ -0,0 +1 @@
Str("newxfoonewxy",[])

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@ -0,0 +1,11 @@
with import ./lib.nix;
let
attrs = {y = "y"; x = "x"; foo = "foo";} // rec {x = "newx"; bar = x;};
names = builtins.attrNames attrs;
values = map (name: builtins.getAttr name attrs) names;
in concat values