From 1a7e88bbd9290987e72616d42c9e9d344acc2a86 Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Tue, 12 Dec 2006 16:14:31 +0000 Subject: [PATCH] * New built-in function `builtins.attrNames' that returns the names of the attributes in an attribute set. --- doc/manual/writing-nix-expressions.xml | 18 ++++++++++++++++++ src/libexpr/primops.cc | 21 +++++++++++++++++++++ tests/lang/eval-okay-attrnames.exp | 1 + tests/lang/eval-okay-attrnames.nix | 11 +++++++++++ 4 files changed, 51 insertions(+) create mode 100644 tests/lang/eval-okay-attrnames.exp create mode 100644 tests/lang/eval-okay-attrnames.nix diff --git a/doc/manual/writing-nix-expressions.xml b/doc/manual/writing-nix-expressions.xml index 1cc5bb95b..9770e9182 100644 --- a/doc/manual/writing-nix-expressions.xml +++ b/doc/manual/writing-nix-expressions.xml @@ -1362,6 +1362,24 @@ is also available as builtins.derivation. + builtins.attrNames + attrs + + Return the names of the attributes in the + attribute set attrs in a sorted list. + For instance, builtins.attrNames {y = 1; x = + "foo";} evaluates to ["x" "y"]. + There is no built-in function attrValues, but + you can easily define it yourself: + + +attrValues = attrs: map (name: builtins.getAttr name attrs) (builtins.attrNames attrs); + + + + + + baseNameOf s Return the base name of the diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc index 1d0d9c6b2..fcf035450 100644 --- a/src/libexpr/primops.cc +++ b/src/libexpr/primops.cc @@ -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); diff --git a/tests/lang/eval-okay-attrnames.exp b/tests/lang/eval-okay-attrnames.exp new file mode 100644 index 000000000..98af99a0c --- /dev/null +++ b/tests/lang/eval-okay-attrnames.exp @@ -0,0 +1 @@ +Str("newxfoonewxy",[]) diff --git a/tests/lang/eval-okay-attrnames.nix b/tests/lang/eval-okay-attrnames.nix new file mode 100644 index 000000000..978138f0c --- /dev/null +++ b/tests/lang/eval-okay-attrnames.nix @@ -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