forked from lix-project/lix
510 lines
14 KiB
C++
510 lines
14 KiB
C++
#include "eval.hh"
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#include "parser.hh"
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#include "nixexpr-ast.hh"
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EvalState::EvalState()
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: normalForms(32768, 50)
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{
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blackHole = makeBlackHole();
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nrEvaluated = nrCached = 0;
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initNixExprHelpers();
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addPrimOps();
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}
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void EvalState::addPrimOp(const string & name,
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unsigned int arity, PrimOp primOp)
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{
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primOps.set(name, makePrimOpDef(arity, ATmakeBlob(0, (void *) primOp)));
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}
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/* Substitute an argument set into the body of a function. */
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static Expr substArgs(Expr body, ATermList formals, Expr arg)
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{
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ATermMap subs(ATgetLength(formals) * 2);
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Expr undefined = makeUndefined();
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/* Get the formal arguments. */
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for (ATermIterator i(formals); i; ++i) {
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Expr name, def;
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if (matchNoDefFormal(*i, name))
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subs.set(name, undefined);
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else if (matchDefFormal(*i, name, def))
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subs.set(name, def);
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else abort(); /* can't happen */
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}
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/* Get the actual arguments, and check that they match with the
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formals. */
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ATermMap args;
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queryAllAttrs(arg, args);
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for (ATermIterator i(args.keys()); i; ++i) {
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Expr key = *i;
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Expr cur = subs.get(key);
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if (!cur)
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throw Error(format("unexpected function argument `%1%'")
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% aterm2String(key));
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subs.set(key, args.get(key));
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}
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/* Check that all arguments are defined. */
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for (ATermIterator i(subs.keys()); i; ++i)
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if (subs.get(*i) == undefined)
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throw Error(format("required function argument `%1%' missing")
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% aterm2String(*i));
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return substitute(subs, body);
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}
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/* Transform a mutually recursive set into a non-recursive set. Each
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attribute is transformed into an expression that has all references
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to attributes substituted with selection expressions on the
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original set. E.g., e = `rec {x = f x y; y = x;}' becomes `{x = f
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(e.x) (e.y); y = e.x;}'. */
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ATerm expandRec(ATerm e, ATermList rbnds, ATermList nrbnds)
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{
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ATerm name;
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Expr e2;
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Pos pos;
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/* Create the substitution list. */
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ATermMap subs;
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for (ATermIterator i(rbnds); i; ++i) {
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if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
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subs.set(name, makeSelect(e, name));
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}
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for (ATermIterator i(nrbnds); i; ++i) {
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if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
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subs.set(name, e2);
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}
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/* Create the non-recursive set. */
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ATermMap as;
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for (ATermIterator i(rbnds); i; ++i) {
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if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
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as.set(name, makeAttrRHS(substitute(subs, e2), pos));
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}
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/* Copy the non-recursive bindings. !!! inefficient */
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for (ATermIterator i(nrbnds); i; ++i) {
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if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
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as.set(name, makeAttrRHS(e2, pos));
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}
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return makeAttrs(as);
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}
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static Expr updateAttrs(Expr e1, Expr e2)
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{
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/* Note: e1 and e2 should be in normal form. */
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ATermMap attrs;
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queryAllAttrs(e1, attrs, true);
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queryAllAttrs(e2, attrs, true);
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return makeAttrs(attrs);
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}
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string evalString(EvalState & state, Expr e)
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{
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e = evalExpr(state, e);
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ATerm s;
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if (!matchStr(e, s)) throw Error("string expected");
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return aterm2String(s);
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}
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Path evalPath(EvalState & state, Expr e)
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{
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e = evalExpr(state, e);
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ATerm s;
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if (!matchPath(e, s)) throw Error("path expected");
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return aterm2String(s);
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}
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bool evalBool(EvalState & state, Expr e)
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{
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e = evalExpr(state, e);
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if (e == eTrue) return true;
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else if (e == eFalse) return false;
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else throw Error("boolean expected");
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}
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ATermList evalList(EvalState & state, Expr e)
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{
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e = evalExpr(state, e);
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ATermList list;
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if (!matchList(e, list)) throw Error("list expected");
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return list;
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}
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/* String concatenation and context nodes: in order to allow users to
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write things like
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"--with-freetype2-library=" + freetype + "/lib"
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where `freetype' is a derivation, we automatically coerce
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derivations into their output path (e.g.,
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/nix/store/hashcode-freetype) in concatenations. However, if we do
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this naively, we could introduce an undeclared dependency: when the
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string is used in another derivation, that derivation would not
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have an explicitly dependency on `freetype' in its inputDrvs
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field. Thus `freetype' would not necessarily be built.
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To prevent this, we wrap the string resulting from the
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concatenation in a *context node*, like this:
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Context([freetype],
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Str("--with-freetype2-library=/nix/store/hashcode-freetype/lib"))
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Thus the context is the list of all derivations used in the
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computation of a value. These contexts are propagated through
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further concatenations. In processBinding() in primops.cc, context
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nodes are unwrapped and added to inputDrvs.
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!!! Should the ordering of the context list have a canonical form?
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!!! Contexts are not currently recognised in most places in the
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evaluator. */
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/* Coerce a value to a string, keeping track of contexts. */
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string coerceToStringWithContext(EvalState & state,
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ATermList & context, Expr e, bool & isPath)
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{
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isPath = false;
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e = evalExpr(state, e);
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ATermList es;
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ATerm e2;
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if (matchContext(e, es, e2)) {
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e = e2;
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context = ATconcat(es, context);
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}
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ATerm s;
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if (matchStr(e, s) || matchUri(e, s))
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return aterm2String(s);
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if (matchPath(e, s)) {
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isPath = true;
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return aterm2String(s);
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}
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if (matchAttrs(e, es)) {
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ATermMap attrs;
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queryAllAttrs(e, attrs, false);
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Expr a = attrs.get("type");
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if (a && evalString(state, a) == "derivation") {
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a = attrs.get("outPath");
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if (!a) throw Error("output path missing from derivation");
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context = ATinsert(context, e);
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return evalPath(state, a);
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}
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}
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throw Error("cannot coerce value to string");
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}
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/* Wrap an expression in a context if the context is not empty. */
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Expr wrapInContext(ATermList context, Expr e)
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{
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return context == ATempty ? e : makeContext(context, e);
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}
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static ATerm concatStrings(EvalState & state, const ATermVector & args)
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{
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ATermList context = ATempty;
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ostringstream s;
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bool isPath;
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for (ATermVector::const_iterator i = args.begin(); i != args.end(); ++i) {
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bool isPath2;
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s << coerceToStringWithContext(state, context, *i, isPath2);
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if (i == args.begin()) isPath = isPath2;
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}
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Expr result = isPath
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? makePath(toATerm(canonPath(s.str())))
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: makeStr(toATerm(s.str()));
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return wrapInContext(context, result);
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}
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Expr evalExpr2(EvalState & state, Expr e)
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{
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Expr e1, e2, e3, e4;
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ATerm name, pos;
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AFun sym = ATgetAFun(e);
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/* Normal forms. */
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if (sym == symStr ||
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sym == symPath ||
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sym == symSubPath ||
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sym == symUri ||
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sym == symNull ||
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sym == symInt ||
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sym == symBool ||
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sym == symFunction ||
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sym == symFunction1 ||
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sym == symAttrs ||
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sym == symList ||
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sym == symPrimOp ||
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sym == symContext)
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return e;
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/* The `Closed' constructor is just a way to prevent substitutions
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into expressions not containing free variables. */
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if (matchClosed(e, e1))
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return evalExpr(state, e1);
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/* Any encountered variables must be primops (since undefined
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variables are detected after parsing). */
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if (matchVar(e, name)) {
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ATerm primOp = state.primOps.get(name);
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if (!primOp)
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throw Error(format("impossible: undefined variable `%1%'") % name);
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int arity;
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ATermBlob fun;
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if (!matchPrimOpDef(primOp, arity, fun)) abort();
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if (arity == 0)
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return ((PrimOp) ATgetBlobData(fun)) (state, ATermVector());
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else
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return makePrimOp(arity, fun, ATempty);
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}
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/* Function application. */
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if (matchCall(e, e1, e2)) {
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ATermList formals;
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ATerm pos;
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/* Evaluate the left-hand side. */
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e1 = evalExpr(state, e1);
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/* Is it a primop or a function? */
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int arity;
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ATermBlob fun;
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ATermList args;
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if (matchPrimOp(e1, arity, fun, args)) {
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args = ATinsert(args, e2);
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if (ATgetLength(args) == arity) {
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/* Put the arguments in a vector in reverse (i.e.,
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actual) order. */
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ATermVector args2(arity);
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for (ATermIterator i(args); i; ++i)
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args2[--arity] = *i;
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return ((PrimOp) ATgetBlobData((ATermBlob) fun))
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(state, args2);
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} else
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/* Need more arguments, so propagate the primop. */
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return makePrimOp(arity, fun, args);
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}
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else if (matchFunction(e1, formals, e4, pos)) {
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e2 = evalExpr(state, e2);
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try {
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return evalExpr(state, substArgs(e4, formals, e2));
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} catch (Error & e) {
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e.addPrefix(format("while evaluating the function at %1%:\n")
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% showPos(pos));
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throw;
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}
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}
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else if (matchFunction1(e1, name, e4, pos)) {
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try {
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ATermMap subs;
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subs.set(name, e2);
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return evalExpr(state, substitute(subs, e4));
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} catch (Error & e) {
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e.addPrefix(format("while evaluating the function at %1%:\n")
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% showPos(pos));
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throw;
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}
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}
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else throw Error("function or primop expected in function call");
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}
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/* Attribute selection. */
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if (matchSelect(e, e1, name)) {
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ATerm pos;
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string s1 = aterm2String(name);
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Expr a = queryAttr(evalExpr(state, e1), s1, pos);
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if (!a) throw Error(format("attribute `%1%' missing") % s1);
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try {
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return evalExpr(state, a);
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} catch (Error & e) {
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e.addPrefix(format("while evaluating the attribute `%1%' at %2%:\n")
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% s1 % showPos(pos));
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throw;
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}
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}
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/* Mutually recursive sets. */
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ATermList rbnds, nrbnds;
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if (matchRec(e, rbnds, nrbnds))
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return expandRec(e, rbnds, nrbnds);
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/* Conditionals. */
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if (matchIf(e, e1, e2, e3)) {
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if (evalBool(state, e1))
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return evalExpr(state, e2);
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else
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return evalExpr(state, e3);
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}
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/* Assertions. */
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if (matchAssert(e, e1, e2, pos)) {
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if (!evalBool(state, e1))
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throw AssertionError(format("assertion failed at %1%") % showPos(pos));
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return evalExpr(state, e2);
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}
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/* Withs. */
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if (matchWith(e, e1, e2, pos)) {
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ATermMap attrs;
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try {
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e1 = evalExpr(state, e1);
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queryAllAttrs(e1, attrs);
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} catch (Error & e) {
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e.addPrefix(format("while evaluating the `with' definitions at %1%:\n")
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% showPos(pos));
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throw;
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}
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try {
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e2 = substitute(attrs, e2);
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checkVarDefs(state.primOps, e2);
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return evalExpr(state, e2);
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} catch (Error & e) {
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e.addPrefix(format("while evaluating the `with' body at %1%:\n")
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% showPos(pos));
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throw;
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}
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}
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/* Generic equality. */
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if (matchOpEq(e, e1, e2))
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return makeBool(evalExpr(state, e1) == evalExpr(state, e2));
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/* Generic inequality. */
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if (matchOpNEq(e, e1, e2))
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return makeBool(evalExpr(state, e1) != evalExpr(state, e2));
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/* Negation. */
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if (matchOpNot(e, e1))
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return makeBool(!evalBool(state, e1));
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/* Implication. */
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if (matchOpImpl(e, e1, e2))
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return makeBool(!evalBool(state, e1) || evalBool(state, e2));
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/* Conjunction (logical AND). */
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if (matchOpAnd(e, e1, e2))
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return makeBool(evalBool(state, e1) && evalBool(state, e2));
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/* Disjunction (logical OR). */
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if (matchOpOr(e, e1, e2))
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return makeBool(evalBool(state, e1) || evalBool(state, e2));
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/* Attribute set update (//). */
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if (matchOpUpdate(e, e1, e2))
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return updateAttrs(evalExpr(state, e1), evalExpr(state, e2));
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/* Attribute existence test (?). */
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if (matchOpHasAttr(e, e1, name)) {
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ATermMap attrs;
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queryAllAttrs(evalExpr(state, e1), attrs);
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return makeBool(attrs.get(name) != 0);
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}
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/* String or path concatenation. */
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if (matchOpPlus(e, e1, e2)) {
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ATermVector args;
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args.push_back(e1);
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args.push_back(e2);
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return concatStrings(state, args);
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}
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/* List concatenation. */
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if (matchOpConcat(e, e1, e2)) {
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ATermList l1 = evalList(state, e1);
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ATermList l2 = evalList(state, e2);
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return makeList(ATconcat(l1, l2));
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}
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/* Barf. */
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throw badTerm("invalid expression", e);
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}
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Expr evalExpr(EvalState & state, Expr e)
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{
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checkInterrupt();
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startNest(nest, lvlVomit,
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format("evaluating expression: %1%") % e);
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state.nrEvaluated++;
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/* Consult the memo table to quickly get the normal form of
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previously evaluated expressions. */
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Expr nf = state.normalForms.get(e);
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if (nf) {
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if (nf == state.blackHole)
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throw Error("infinite recursion encountered");
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state.nrCached++;
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return nf;
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}
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/* Otherwise, evaluate and memoize. */
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state.normalForms.set(e, state.blackHole);
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try {
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nf = evalExpr2(state, e);
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} catch (Error & err) {
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debug("removing black hole");
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state.normalForms.remove(e);
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throw;
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}
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state.normalForms.set(e, nf);
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return nf;
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}
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Expr evalFile(EvalState & state, const Path & path)
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{
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startNest(nest, lvlTalkative, format("evaluating file `%1%'") % path);
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Expr e = parseExprFromFile(state, path);
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try {
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return evalExpr(state, e);
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} catch (Error & e) {
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e.addPrefix(format("while evaluating the file `%1%':\n")
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% path);
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throw;
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}
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}
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void printEvalStats(EvalState & state)
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{
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debug(format("evaluated %1% expressions, %2% cache hits, %3%%% efficiency")
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% state.nrEvaluated % state.nrCached
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% ((float) state.nrCached / (float) state.nrEvaluated * 100));
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}
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