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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;
typedef struct Env_ * Env;
typedef struct Value_ * Value;
typedef std::map<string, Value> Bindings;
struct Env_
{
Env up;
Bindings bindings;
};
typedef enum {
tInt = 1,
tAttrs,
tThunk,
tLambda
} ValueType;
struct Value_
{
ValueType type;
union
{
int integer;
Bindings * attrs;
struct {
Env env;
Expr expr;
} thunk;
struct {
Env env;
Pattern pat;
Expr body;
} lambda;
};
};
std::ostream & operator << (std::ostream & str, Value_ & v)
{
switch (v.type) {
case tInt:
str << v.integer;
break;
case tAttrs:
str << "{ ";
foreach (Bindings::iterator, i, *v.attrs) {
str << i->first << " = " << *i->second << "; ";
}
str << "}";
break;
case tThunk:
str << "<CODE>";
break;
default:
abort();
}
return str;
}
Value eval(Env env, Expr e);
void forceValue(Value v)
{
if (v->type != tThunk) return;
Value v2 = eval(v->thunk.env, v->thunk.expr);
*v = *v2; // !!! slightly inefficient
}
Value lookupVar(Env env, const string & name)
{
for ( ; env; env = env->up) {
Value v = env->bindings[name];
if (v) return v;
}
throw Error("undefined variable");
}
Value eval(Env env, Expr e)
{
printMsg(lvlError, format("eval: %1%") % e);
ATerm name;
if (matchVar(e, name)) {
Value v = lookupVar(env, aterm2String(name));
forceValue(v);
return v;
}
int n;
if (matchInt(e, n)) {
Value v = new Value_;
v->type = tInt;
v->integer = n;
return v;
}
ATermList es;
if (matchAttrs(e, es)) {
Value v = new Value_;
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 = new Value_;
v2->type = tThunk;
v2->thunk.env = env;
v2->thunk.expr = e2;
(*v->attrs)[aterm2String(name)] = v2;
}
return v;
}
ATermList rbnds, nrbnds;
if (matchRec(e, rbnds, nrbnds)) {
Env env2 = new Env_;
env2->up = env;
Value v = new Value_;
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 = new Value_;
v2->type = tThunk;
v2->thunk.env = env2;
v2->thunk.expr = e2;
env2->bindings[aterm2String(name)] = v2;
}
return v;
}
Expr e2;
if (matchSelect(e, e2, name)) {
Value v = eval(env, e2);
if (v->type != tAttrs) throw TypeError("expected attribute set");
Value v2 = (*v->attrs)[aterm2String(name)];
if (!v2) throw TypeError("attribute not found");
forceValue(v2);
return v2;
}
Pattern pat; Expr body; Pos pos;
if (matchFunction(e, pat, body, pos)) {
Value v = new Value_;
v->type = tLambda;
v->lambda.env = env;
v->lambda.pat = pat;
v->lambda.body = body;
return v;
}
Expr fun, arg;
if (matchCall(e, fun, arg)) {
Value fun_ = eval(env, fun);
if (fun_->type != tLambda) throw TypeError("expected function");
if (!matchVarPat(fun_->lambda.pat, name)) throw Error("not implemented");
Value arg_ = new Value_;
arg_->type = tThunk;
arg_->thunk.env = env;
arg_->thunk.expr = arg;
Env env2 = new Env_;
env2->up = env;
env2->bindings[aterm2String(name)] = arg_;
return eval(env2, fun_->lambda.body);
}
abort();
}
void doTest(string s)
{
EvalState state;
Expr e = parseExprFromString(state, s, "/");
printMsg(lvlError, format("%1%") % e);
Value v = eval(0, e);
printMsg(lvlError, format("result: %1%") % *v);
}
void run(Strings args)
{
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");
doTest("(x: x) 1");
doTest("(x: y: y) 1 2");
//Expr e = parseExprFromString(state, "let x = \"a\"; in x + \"b\"", "/");
//Expr e = parseExprFromString(state, "(x: x + \"b\") \"a\"", "/");
//Expr e = parseExprFromString(state, "\"a\" + \"b\"", "/");
//Expr e = parseExprFromString(state, "\"a\" + \"b\"", "/");
}
void printHelp()
{
}
string programId = "eval-test";
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