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Add primop ‘catAttrs’
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3 changed files with 32 additions and 0 deletions
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@ -1123,6 +1123,35 @@ static void prim_intersectAttrs(EvalState & state, const Pos & pos, Value * * ar
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}
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/* Collect each attribute named `attr' from a list of attribute sets.
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Sets that don't contain the named attribute are ignored.
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Example:
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catAttrs "a" [{a = 1;} {b = 0;} {a = 2;}]
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=> [1 2]
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*/
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static void prim_catAttrs(EvalState & state, const Pos & pos, Value * * args, Value & v)
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{
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Symbol attrName = state.symbols.create(state.forceStringNoCtx(*args[0], pos));
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state.forceList(*args[1], pos);
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Value * res[args[1]->list.length];
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unsigned int found = 0;
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for (unsigned int n = 0; n < args[1]->list.length; ++n) {
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Value & v2(*args[1]->list.elems[n]);
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state.forceAttrs(v2, pos);
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Bindings::iterator i = v2.attrs->find(attrName);
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if (i != v2.attrs->end())
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res[found++] = i->value;
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}
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state.mkList(v, found);
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for (unsigned int n = 0; n < found; ++n)
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v.list.elems[n] = res[n];
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}
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/* Return a set containing the names of the formal arguments expected
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by the function `f'. The value of each attribute is a Boolean
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denoting whether has a default value. For instance,
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@ -1530,6 +1559,7 @@ void EvalState::createBaseEnv()
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addPrimOp("removeAttrs", 2, prim_removeAttrs);
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addPrimOp("__listToAttrs", 1, prim_listToAttrs);
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addPrimOp("__intersectAttrs", 2, prim_intersectAttrs);
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addPrimOp("__catAttrs", 2, prim_catAttrs);
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addPrimOp("__functionArgs", 1, prim_functionArgs);
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// Lists
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1
tests/lang/eval-okay-catattrs.exp
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1
tests/lang/eval-okay-catattrs.exp
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@ -0,0 +1 @@
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[ 1 2 ]
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1
tests/lang/eval-okay-catattrs.nix
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1
tests/lang/eval-okay-catattrs.nix
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@ -0,0 +1 @@
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builtins.catAttrs "a" [ { a = 1; } { b = 0; } { a = 2; } ]
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