From 7482349fe8ba9f285f6c7e53d8573fc367ecff8b Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Wed, 24 Mar 2010 23:40:00 +0000
Subject: [PATCH] * Implemented attribute set pattern matches.

---
 src/libexpr/eval-test.cc | 130 +++++++++++++++++++++++++++++++++++----
 1 file changed, 117 insertions(+), 13 deletions(-)

diff --git a/src/libexpr/eval-test.cc b/src/libexpr/eval-test.cc
index 68a7380e5d..27cf685f9d 100644
--- a/src/libexpr/eval-test.cc
+++ b/src/libexpr/eval-test.cc
@@ -26,7 +26,8 @@ typedef enum {
     tInt = 1,
     tAttrs,
     tThunk,
-    tLambda
+    tLambda,
+    tCopy
 } ValueType;
 
 
@@ -46,6 +47,7 @@ struct Value
             Pattern pat;
             Expr body;
         } lambda;
+        Value * val;
     };
 };
 
@@ -65,6 +67,9 @@ std::ostream & operator << (std::ostream & str, Value & v)
     case tThunk:
         str << "<CODE>";
         break;
+    case tLambda:
+        str << "<LAMBDA>";
+        break;
     default:
         abort();
     }
@@ -72,13 +77,16 @@ std::ostream & operator << (std::ostream & str, Value & v)
 }
 
 
-void eval(Env * env, Expr e, Value & v);
+static void eval(Env * env, Expr e, Value & v);
 
 
 void forceValue(Value & v)
 {
-    if (v.type != tThunk) return;
-    eval(v.thunk.env, v.thunk.expr, v);
+    if (v.type == tThunk) eval(v.thunk.env, v.thunk.expr, v);
+    else if (v.type == tCopy) {
+        forceValue(*v.val);
+        v = *v.val;
+    }
 }
 
 
@@ -103,7 +111,92 @@ Env * allocEnv()
 }
 
 
-void eval(Env * env, Expr e, Value & v)
+static bool patternIsStrict(Pattern pat)
+{
+    ATerm name, ellipsis, pat1, pat2;
+    ATermList formals;
+    if (matchVarPat(pat, name)) return false;
+    else if (matchAttrsPat(pat, formals, ellipsis)) return true;
+    else if (matchAtPat(pat, pat1, pat2))
+        return patternIsStrict(pat1) || patternIsStrict(pat2);
+    else abort();
+}
+
+
+static void bindVarPats(Pattern pat, Env & newEnv,
+    Env * argEnv, Expr argExpr, Value * & vArg)
+{
+    Pattern pat1, pat2;
+    if (matchAtPat(pat, pat1, pat2)) {
+        bindVarPats(pat1, newEnv, argEnv, argExpr, vArg);
+        bindVarPats(pat2, newEnv, argEnv, argExpr, vArg);
+        return;
+    }
+
+    ATerm name;
+    if (!matchVarPat(pat, name)) abort();
+
+    if (vArg) {
+        Value & v = newEnv.bindings[aterm2String(name)];
+        v.type = tCopy;
+        v.val = vArg;
+    } else {
+        vArg = &newEnv.bindings[aterm2String(name)];
+        vArg->type = tThunk;
+        vArg->thunk.env = argEnv;
+        vArg->thunk.expr = argExpr;
+    }
+}
+
+
+static void bindAttrPats(Pattern pat, Env & newEnv,
+    Value & vArg, Value * & vArgInEnv)
+{
+    Pattern pat1, pat2;
+    if (matchAtPat(pat, pat1, pat2)) {
+        bindAttrPats(pat1, newEnv, vArg, vArgInEnv);
+        bindAttrPats(pat2, newEnv, vArg, vArgInEnv);
+        return;
+    }
+    
+    ATerm name;
+    if (matchVarPat(pat, name)) {
+        if (vArgInEnv) {
+            Value & v = newEnv.bindings[aterm2String(name)];
+            v.type = tCopy;
+            v.val = vArgInEnv;
+        } else {
+            vArgInEnv = &newEnv.bindings[aterm2String(name)];
+            *vArgInEnv = vArg;
+        }
+        return;
+    }
+
+    ATerm ellipsis;
+    ATermList formals;
+    if (matchAttrsPat(pat, formals, ellipsis)) {
+        for (ATermIterator i(formals); i; ++i) {
+            Expr name, def;
+            DefaultValue def2;
+            if (!matchFormal(*i, name, def2)) abort(); /* can't happen */
+
+            Bindings::iterator j = vArg.attrs->find(aterm2String(name));
+            if (j == vArg.attrs->end())
+                throw TypeError(format("the argument named `%1%' required by the function is missing")
+                    % aterm2String(name));
+            
+            Value & v = newEnv.bindings[aterm2String(name)];
+            v.type = tCopy;
+            v.val = &j->second;
+        }
+        return;
+    }
+
+    abort();
+}
+
+
+static void eval(Env * env, Expr e, Value & v)
 {
     printMsg(lvlError, format("eval: %1%") % e);
 
@@ -182,17 +275,21 @@ void eval(Env * env, Expr e, Value & v)
     if (matchCall(e, fun, arg)) {
         eval(env, fun, v);
         if (v.type != tLambda) throw TypeError("expected function");
-        if (!matchVarPat(v.lambda.pat, name)) throw Error("not implemented");
 
         Env * env2 = allocEnv();
         env2->up = env;
-        
-        Value & arg_ = env2->bindings[aterm2String(name)];
-        nrValues++;
-        arg_.type = tThunk;
-        arg_.thunk.env = env;
-        arg_.thunk.expr = arg;
 
+        if (patternIsStrict(v.lambda.pat)) {
+            Value vArg;
+            eval(env, arg, vArg);
+            if (vArg.type != tAttrs) throw TypeError("expected attribute set");
+            Value * vArg2 = 0;
+            bindAttrPats(v.lambda.pat, *env2, vArg, vArg2);
+        } else {
+            Value * vArg = 0;
+            bindVarPats(v.lambda.pat, *env2, env, arg, vArg);
+        }
+        
         eval(env2, v.lambda.body, v);
         return;
     }
@@ -205,7 +302,7 @@ void doTest(string s)
 {
     EvalState state;
     Expr e = parseExprFromString(state, s, "/");
-    printMsg(lvlError, format("%1%") % e);
+    printMsg(lvlError, format(">>>>> %1%") % e);
     Value v;
     eval(0, e, v);
     printMsg(lvlError, format("result: %1%") % v);
@@ -222,6 +319,13 @@ void run(Strings args)
     doTest("rec { x = 1; y = x; }.y");
     doTest("(x: x) 1");
     doTest("(x: y: y) 1 2");
+    doTest("(x@y: x) 1");
+    doTest("(x@y: y) 2");
+    doTest("(x@y@z: y) 3");
+    doTest("x: x");
+    doTest("({x, y}: x) { x = 1; y = 2; }");
+    doTest("({x, y}@args: args.x) { x = 1; y = 2; }");
+    doTest("({x, y}@args@args2: args2.x) { x = 1; y = 2; }");
     
     //Expr e = parseExprFromString(state, "let x = \"a\"; in x + \"b\"", "/");
     //Expr e = parseExprFromString(state, "(x: x + \"b\") \"a\"", "/");