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#include "eval.hh"
#include "expr.hh"
#include "parser.hh"
#include "primops.hh"
EvalState::EvalState()
{
blackHole = ATmake("BlackHole()");
if (!blackHole) throw Error("cannot build black hole");
nrEvaluated = nrCached = 0;
}
Expr getAttr(EvalState & state, Expr e, const string & name)
{
}
/* Substitute an argument set into the body of a function. */
static Expr substArgs(Expr body, ATermList formals, Expr arg)
{
Subs subs;
Expr undefined = ATmake("Undefined");
/* Get the formal arguments. */
while (!ATisEmpty(formals)) {
char * s;
if (!ATmatch(ATgetFirst(formals), "<str>", &s))
abort(); /* can't happen */
subs[s] = undefined;
formals = ATgetNext(formals);
}
/* Get the actual arguments, and check that they match with the
formals. */
Attrs args;
queryAllAttrs(arg, args);
for (Attrs::iterator i = args.begin(); i != args.end(); i++) {
if (subs.find(i->first) == subs.end())
throw badTerm(format("argument `%1%' not declared") % i->first, arg);
subs[i->first] = i->second;
}
/* Check that all arguments are defined. */
for (Subs::iterator i = subs.begin(); i != subs.end(); i++)
if (i->second == undefined)
throw badTerm(format("formal argument `%1%' missing") % i->first, arg);
return substitute(subs, body);
}
/* Transform a mutually recursive set into a non-recursive set. Each
attribute is transformed into an expression that has all references
to attributes substituted with selection expressions on the
original set. E.g., e = `rec {x = f x y, y = x}' becomes `{x = f
(e.x) (e.y), y = e.x}'. */
ATerm expandRec(ATerm e, ATermList bnds)
{
/* Create the substitution list. */
Subs subs;
ATermList bs = bnds;
while (!ATisEmpty(bs)) {
char * s;
Expr e2;
if (!ATmatch(ATgetFirst(bs), "Bind(<str>, <term>)", &s, &e2))
abort(); /* can't happen */
subs[s] = ATmake("Select(<term>, <str>)", e, s);
bs = ATgetNext(bs);
}
/* Create the non-recursive set. */
Attrs as;
bs = bnds;
while (!ATisEmpty(bs)) {
char * s;
Expr e2;
if (!ATmatch(ATgetFirst(bs), "Bind(<str>, <term>)", &s, &e2))
abort(); /* can't happen */
as[s] = substitute(subs, e2);
bs = ATgetNext(bs);
}
return makeAttrs(as);
}
string evalString(EvalState & state, Expr e)
{
e = evalExpr(state, e);
char * s;
if (!ATmatch(e, "Str(<str>)", &s))
throw badTerm("string expected", e);
return s;
}
Path evalPath(EvalState & state, Expr e)
{
e = evalExpr(state, e);
char * s;
if (!ATmatch(e, "Path(<str>)", &s))
throw badTerm("path expected", e);
return s;
}
Expr evalExpr2(EvalState & state, Expr e)
{
Expr e1, e2, e3, e4;
char * s1;
/* Normal forms. */
if (ATmatch(e, "Str(<str>)", &s1) ||
ATmatch(e, "Path(<str>)", &s1) ||
ATmatch(e, "Uri(<str>)", &s1) ||
ATmatch(e, "Function([<list>], <term>)", &e1, &e2) ||
ATmatch(e, "Attrs([<list>])", &e1) ||
ATmatch(e, "List([<list>])", &e1))
return e;
/* Any encountered variables must be undeclared or primops. */
if (ATmatch(e, "Var(<str>)", &s1)) {
return e;
}
/* Function application. */
if (ATmatch(e, "Call(<term>, <term>)", &e1, &e2)) {
/* Evaluate the left-hand side. */
e1 = evalExpr(state, e1);
/* Is it a primop or a function? */
if (ATmatch(e1, "Var(<str>)", &s1)) {
string primop(s1);
if (primop == "import") return primImport(state, e2);
if (primop == "derivation") return primDerivation(state, e2);
else throw badTerm("undefined variable/primop", e1);
}
else if (ATmatch(e1, "Function([<list>], <term>)", &e3, &e4)) {
return evalExpr(state,
substArgs(e4, (ATermList) e3, evalExpr(state, e2)));
}
else throw badTerm("expecting a function or primop", e1);
}
/* Attribute selection. */
if (ATmatch(e, "Select(<term>, <str>)", &e1, &s1)) {
string name(s1);
Expr a = queryAttr(evalExpr(state, e1), name);
if (!a) throw badTerm(format("missing attribute `%1%'") % name, e);
return evalExpr(state, a);
}
/* Mutually recursive sets. */
ATermList bnds;
if (ATmatch(e, "Rec([<list>])", &bnds))
return expandRec(e, (ATermList) bnds);
/* Barf. */
throw badTerm("invalid expression", e);
}
Expr evalExpr(EvalState & state, Expr e)
{
Nest nest(lvlVomit, format("evaluating expression: %1%") % printTerm(e));
state.nrEvaluated++;
/* Consult the memo table to quickly get the normal form of
previously evaluated expressions. */
NormalForms::iterator i = state.normalForms.find(e);
if (i != state.normalForms.end()) {
if (i->second == state.blackHole)
throw badTerm("infinite recursion", e);
state.nrCached++;
return i->second;
}
/* Otherwise, evaluate and memoize. */
state.normalForms[e] = state.blackHole;
Expr nf = evalExpr2(state, e);
state.normalForms[e] = nf;
return nf;
}
Expr evalFile(EvalState & state, const Path & path)
{
Nest nest(lvlTalkative, format("evaluating file `%1%'") % path);
Expr e = parseExprFromFile(path);
return evalExpr(state, e);
}
void printEvalStats(EvalState & state)
{
debug(format("evaluated %1% expressions, %2% cache hits, %3%%% efficiency")
% state.nrEvaluated % state.nrCached
% ((float) state.nrCached / (float) state.nrEvaluated * 100));
}
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