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primop functions listToAttrs (+test), __isAttrs, __trace added
new configuration style proposal in lib/default-unstable.nix
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@ -296,6 +296,17 @@ static Expr prim_getEnv(EvalState & state, const ATermVector & args)
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return makeStr(getEnv(name));
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}
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/* for debugging purposes. print the first arg on stdout (perhaps stderr should be used?)
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* and return the second
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*/
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static Expr prim_trace(EvalState & state, const ATermVector & args)
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{
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//string str = evalStringNoCtx(state, args[0]);
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Expr a = evalExpr(state, args[0]);
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printf("traced value: %s\n", atPrint(a).c_str());
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return evalExpr(state, args[1]);
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}
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static Expr prim_relativise(EvalState & state, const ATermVector & args)
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{
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@ -744,6 +755,39 @@ static Expr prim_hasAttr(EvalState & state, const ATermVector & args)
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}
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/* takes
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* param: list of { attr="attr"; value=value }
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* returns an attribute set
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* */
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static Expr prim_listToAttrs(EvalState & state, const ATermVector & args)
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{
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try {
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ATermMap res = ATermMap();
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ATermList list;
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list = evalList(state, args[0]);
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for (ATermIterator i(list); i; ++i){
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// *i should now contain a pointer to the list item expression
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ATermList attrs;
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Expr evaledExpr = evalExpr(state, *i);
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if (matchAttrs(evaledExpr, attrs)){
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Expr e = evalExpr(state, makeSelect(evaledExpr, toATerm("attr")));
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string attr = evalStringNoCtx(state,e);
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ATerm value;
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Expr r = makeSelect(evaledExpr, toATerm("value"));
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res.set(toATerm(attr), makeAttrRHS(r, makeNoPos()));
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}
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else {
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throw EvalError(format("passed list item is a %s (value: %s). Set { attr=\"name\"; value=nix expr; } expected.") % showType(evaledExpr) % showValue(evaledExpr));
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}
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} // for
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return makeAttrs(res);
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} catch (Error & e) {
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e.addPrefix(format("while calling listToAttrs "));
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throw;
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}
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}
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static Expr prim_removeAttrs(EvalState & state, const ATermVector & args)
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{
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ATermMap attrs;
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@ -758,6 +802,12 @@ static Expr prim_removeAttrs(EvalState & state, const ATermVector & args)
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return makeAttrs(attrs);
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}
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/* Determine whether the argument is a list. */
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static Expr prim_isAttrs(EvalState & state, const ATermVector & args)
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{
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ATermList list;
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return makeBool(matchAttrs(evalExpr(state, args[0]), list));
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}
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/*************************************************************
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* Lists
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@ -901,6 +951,7 @@ void EvalState::addPrimOps()
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addPrimOp("abort", 1, prim_abort);
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addPrimOp("throw", 1, prim_throw);
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addPrimOp("__getEnv", 1, prim_getEnv);
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addPrimOp("__trace", 2, prim_trace);
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addPrimOp("relativise", 2, prim_relativise);
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@ -923,7 +974,9 @@ void EvalState::addPrimOps()
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addPrimOp("__attrNames", 1, prim_attrNames);
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addPrimOp("__getAttr", 2, prim_getAttr);
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addPrimOp("__hasAttr", 2, prim_hasAttr);
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addPrimOp("__isAttrs", 1, prim_isAttrs);
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addPrimOp("removeAttrs", 2, prim_removeAttrs);
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addPrimOp("__listToAttrs", 1, prim_listToAttrs);
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// Lists
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addPrimOp("__isList", 1, prim_isList);
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8
tests/lang/eval-okay-listToAttrs.nix
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8
tests/lang/eval-okay-listToAttrs.nix
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@ -0,0 +1,8 @@
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# this test shows how to use listToAttrs and that evaluation is still lazy (throw isn't called)
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let
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asi = attr: value : { inherit attr value; };
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list = [ ( asi "a" "A" ) ( asi "b" "B" ) ];
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a = builtins.listToAttrs list;
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b = builtins.listToAttrs ( list ++ list );
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r = builtins.listToAttrs [ (asi "result" [ a b ]) ( asi "throw" (throw "this should not be thrown")) ];
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in r.result
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1
tests/lang/eval-okay-listToAttrs.out
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1
tests/lang/eval-okay-listToAttrs.out
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@ -0,0 +1 @@
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List([Attrs([Bind("a",Str("A",[]),NoPos),Bind("b",Str("B",[]),NoPos)]),Attrs([Bind("a",Str("A",[]),NoPos),Bind("b",Str("B",[]),NoPos)])])
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