lix/src/libexpr/eval-test.cc

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#include "nixexpr.hh"
#include "parser.hh"
#include "hash.hh"
#include "util.hh"
#include "nixexpr-ast.hh"
#include <cstdlib>
using namespace nix;
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struct Env;
struct Value;
typedef ATerm Sym;
typedef std::map<Sym, Value> Bindings;
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struct Env
{
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Env * up;
Bindings bindings;
};
typedef enum {
tInt = 1,
tAttrs,
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tList,
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tThunk,
tLambda,
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tCopy,
tBlackhole
} ValueType;
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struct Value
{
ValueType type;
union
{
int integer;
Bindings * attrs;
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struct {
unsigned int length;
Value * elems;
} list;
struct {
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Env * env;
Expr expr;
} thunk;
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struct {
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Env * env;
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Pattern pat;
Expr body;
} lambda;
Value * val;
};
};
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std::ostream & operator << (std::ostream & str, Value & v)
{
switch (v.type) {
case tInt:
str << v.integer;
break;
case tAttrs:
str << "{ ";
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foreach (Bindings::iterator, i, *v.attrs)
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str << aterm2String(i->first) << " = " << i->second << "; ";
str << "}";
break;
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case tList:
str << "[ ";
for (unsigned int n = 0; n < v.list.length; ++n)
str << v.list.elems[n] << " ";
str << "]";
break;
case tThunk:
str << "<CODE>";
break;
case tLambda:
str << "<LAMBDA>";
break;
default:
abort();
}
return str;
}
static void eval(Env * env, Expr e, Value & v);
static void forceValue(Value & v)
{
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if (v.type == tThunk) {
v.type = tBlackhole;
eval(v.thunk.env, v.thunk.expr, v);
}
else if (v.type == tCopy) {
forceValue(*v.val);
v = *v.val;
}
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else if (v.type == tBlackhole)
throw EvalError("infinite recursion encountered");
}
static Value * lookupWith(Env * env, Sym name)
{
if (!env) return 0;
Value * v = lookupWith(env->up, name);
if (v) return v;
Bindings::iterator i = env->bindings.find(sWith);
if (i == env->bindings.end()) return 0;
Bindings::iterator j = i->second.attrs->find(name);
if (j != i->second.attrs->end()) return &j->second;
return 0;
}
static Value * lookupVar(Env * env, Sym name)
{
/* First look for a regular variable binding for `name'. */
for (Env * env2 = env; env2; env2 = env2->up) {
Bindings::iterator i = env2->bindings.find(name);
if (i != env2->bindings.end()) return &i->second;
}
/* Otherwise, look for a `with' attribute set containing `name'.
Outer `withs' take precedence (i.e. `with {x=1;}; with {x=2;};
x' evaluates to 1). */
Value * v = lookupWith(env, name);
if (v) return v;
/* Alternative implementation where the inner `withs' take
precedence (i.e. `with {x=1;}; with {x=2;}; x' evaluates to
2). */
#if 0
for (Env * env2 = env; env2; env2 = env2->up) {
Bindings::iterator i = env2->bindings.find(sWith);
if (i == env2->bindings.end()) continue;
Bindings::iterator j = i->second.attrs->find(name);
if (j != i->second.attrs->end()) return &j->second;
}
#endif
throw Error("undefined variable");
}
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unsigned long nrValues = 0, nrEnvs = 0;
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static Env * allocEnv()
{
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nrEnvs++;
return new Env;
}
static void eval(Env * env, Expr e, Value & v)
{
printMsg(lvlError, format("eval: %1%") % e);
Sym name;
if (matchVar(e, name)) {
Value * v2 = lookupVar(env, name);
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forceValue(*v2);
v = *v2;
return;
}
int n;
if (matchInt(e, n)) {
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v.type = tInt;
v.integer = n;
return;
}
ATermList es;
if (matchAttrs(e, es)) {
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v.type = tAttrs;
v.attrs = new Bindings;
ATerm e2, pos;
for (ATermIterator i(es); i; ++i) {
if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
Value & v2 = (*v.attrs)[name];
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nrValues++;
v2.type = tThunk;
v2.thunk.env = env;
v2.thunk.expr = e2;
}
return;
}
ATermList rbnds, nrbnds;
if (matchRec(e, rbnds, nrbnds)) {
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Env * env2 = allocEnv();
env2->up = env;
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v.type = tAttrs;
v.attrs = &env2->bindings;
ATerm name, e2, pos;
for (ATermIterator i(rbnds); i; ++i) {
if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
Value & v2 = env2->bindings[name];
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nrValues++;
v2.type = tThunk;
v2.thunk.env = env2;
v2.thunk.expr = e2;
}
return;
}
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Expr e1, e2;
if (matchSelect(e, e2, name)) {
eval(env, e2, v);
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if (v.type != tAttrs) throw TypeError("expected attribute set");
Bindings::iterator i = v.attrs->find(name);
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if (i == v.attrs->end()) throw TypeError("attribute not found");
forceValue(i->second);
v = i->second;
return;
}
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Pattern pat; Expr body; Pos pos;
if (matchFunction(e, pat, body, pos)) {
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v.type = tLambda;
v.lambda.env = env;
v.lambda.pat = pat;
v.lambda.body = body;
return;
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}
Expr fun, arg;
if (matchCall(e, fun, arg)) {
eval(env, fun, v);
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if (v.type != tLambda) throw TypeError("expected function");
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Env * env2 = allocEnv();
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env2->up = env;
ATermList formals; ATerm ellipsis;
if (matchVarPat(v.lambda.pat, name)) {
Value & vArg = env2->bindings[name];
vArg.type = tThunk;
vArg.thunk.env = env;
vArg.thunk.expr = arg;
}
else if (matchAttrsPat(v.lambda.pat, formals, ellipsis, name)) {
Value * vArg;
Value vArg_;
if (name == sNoAlias)
vArg = &vArg_;
else
vArg = &env2->bindings[name];
eval(env, arg, *vArg);
if (vArg->type != tAttrs) throw TypeError("expected attribute set");
/* For each formal argument, get the actual argument. If
there is no matching actual argument but the formal
argument has a default, use the default. */
unsigned int attrsUsed = 0;
for (ATermIterator i(formals); i; ++i) {
Expr def; Sym name;
DefaultValue def2;
if (!matchFormal(*i, name, def2)) abort(); /* can't happen */
Bindings::iterator j = vArg->attrs->find(name);
Value & v = env2->bindings[name];
if (j == vArg->attrs->end()) {
if (!matchDefaultValue(def2, def)) def = 0;
if (def == 0) throw TypeError(format("the argument named `%1%' required by the function is missing")
% aterm2String(name));
v.type = tThunk;
v.thunk.env = env2;
v.thunk.expr = def;
} else {
attrsUsed++;
v.type = tCopy;
v.val = &j->second;
}
}
/* Check that each actual argument is listed as a formal
argument (unless the attribute match specifies a
`...'). TODO: show the names of the
expected/unexpected arguments. */
if (ellipsis == eFalse && attrsUsed != vArg->attrs->size())
throw TypeError("function called with unexpected argument");
}
else abort();
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eval(env2, v.lambda.body, v);
return;
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}
Expr attrs;
if (matchWith(e, attrs, body, pos)) {
Env * env2 = allocEnv();
env2->up = env;
Value & vAttrs = env2->bindings[sWith];
eval(env, attrs, vAttrs);
if (vAttrs.type != tAttrs) throw TypeError("`with' should evaluate to an attribute set");
eval(env2, body, v);
return;
}
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if (matchList(e, es)) {
v.type = tList;
v.list.length = ATgetLength(es);
v.list.elems = new Value[v.list.length]; // !!! check destructor
for (unsigned int n = 0; n < v.list.length; ++n, es = ATgetNext(es)) {
v.list.elems[n].type = tThunk;
v.list.elems[n].thunk.env = env;
v.list.elems[n].thunk.expr = ATgetFirst(es);
}
return;
}
if (matchOpConcat(e, e1, e2)) {
Value v1; eval(env, e1, v1);
if (v1.type != tList) throw TypeError("list expecteed");
Value v2; eval(env, e2, v2);
if (v2.type != tList) throw TypeError("list expecteed");
v.type = tList;
v.list.length = v1.list.length + v2.list.length;
v.list.elems = new Value[v.list.length];
/* !!! This loses sharing with the original lists. We could
use a tCopy node, but that would use more memory. */
for (unsigned int n = 0; n < v1.list.length; ++n)
v.list.elems[n] = v1.list.elems[n];
for (unsigned int n = 0; n < v2.list.length; ++n)
v.list.elems[n + v1.list.length] = v2.list.elems[n];
return;
}
throw Error("unsupported term");
}
static void strictEval(Env * env, Expr e, Value & v)
{
eval(env, e, v);
if (v.type == tAttrs) {
foreach (Bindings::iterator, i, *v.attrs)
forceValue(i->second);
}
else if (v.type == tList) {
for (unsigned int n = 0; n < v.list.length; ++n)
forceValue(v.list.elems[n]);
}
}
void doTest(string s)
{
EvalState state;
Expr e = parseExprFromString(state, s, "/");
printMsg(lvlError, format(">>>>> %1%") % e);
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Value v;
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strictEval(0, e, v);
printMsg(lvlError, format("result: %1%") % v);
}
void run(Strings args)
{
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printMsg(lvlError, format("size of value: %1% bytes") % sizeof(Value));
doTest("123");
doTest("{ x = 1; y = 2; }");
doTest("{ x = 1; y = 2; }.y");
doTest("rec { x = 1; y = x; }.y");
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doTest("(x: x) 1");
doTest("(x: y: y) 1 2");
doTest("x: x");
doTest("({x, y}: x) { x = 1; y = 2; }");
doTest("({x, y}@args: args.x) { x = 1; y = 2; }");
doTest("(args@{x, y}: args.x) { x = 1; y = 2; }");
doTest("({x ? 1}: x) { }");
doTest("({x ? 1, y ? x}: y) { x = 2; }");
doTest("({x, y, ...}: x) { x = 1; y = 2; z = 3; }");
doTest("({x, y, ...}@args: args.z) { x = 1; y = 2; z = 3; }");
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//doTest("({x ? y, y ? x}: y) { }");
doTest("let x = 1; in x");
doTest("with { x = 1; }; x");
doTest("let x = 2; in with { x = 1; }; x"); // => 2
doTest("with { x = 1; }; with { x = 2; }; x"); // => 1
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doTest("[ 1 2 3 ]");
doTest("[ 1 2 ] ++ [ 3 4 5 ]");
printMsg(lvlError, format("alloced %1% values") % nrValues);
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printMsg(lvlError, format("alloced %1% environments") % nrEnvs);
}
void printHelp()
{
}
string programId = "eval-test";