Make `last` work

3 files changed, 40 insertions, 16 deletions

diff --git a/environment.cpp b/environment.cpp
index b38d73b..e375353 100644
--- a/environment.cpp
+++ b/environment.cpp
@@ -146,6 +146,11 @@ static void singlify(AST &ast){
 }
 
 bool Environment::resolve(AST &ast){
+	unordered_set<Name> avoid;
+	return resolve(ast,avoid);
+}
+
+bool Environment::resolve(AST &ast,unordered_set<Name> &avoid){
 	if(ast.quoted){
 		return false;
 	}
@@ -160,23 +165,26 @@ bool Environment::resolve(AST &ast){
 			break;
 
 		case AST::Type::name:
-			try {
-				ast=get(ast.nameval);
-				resolve(ast);
-				ret=true;
-			} catch(NameError){
-				// just leave an unknown name as it is
+			if(avoid.find(ast.nameval)==avoid.end()){
+				try {
+					avoid.insert(ast.nameval);
+					ast=get(ast.nameval);
+					resolve(ast,avoid);
+					ret=true;
+				} catch(NameError){
+					// just leave an unknown name as it is
+				}
 			}
 			break;
 
 		case AST::Type::tuple:
 			for(AST &term : ast.terms){
-				ret=resolve(term)||ret;
+				ret=resolve(term,avoid)||ret;
 			}
 			break;
 
 		case AST::Type::lambda:
-			ret=resolve(*ast.lambdaval.body)||ret;
+			ret=resolve(*ast.lambdaval.body,avoid)||ret;
 			break;
 	}
 
@@ -409,6 +417,7 @@ bool Environment::reduce(AST &ast,i64 depth){
 				ret=reduce(ast.terms[1],depth+1)||ret;
 				if(!hasFree(ast.terms[1],1)){
 					ast=ast.terms[0].nativeval(ast.terms[1]);
+					reduce(ast,depth+1);
 					ret=true;
 				} else {
 					cerr<<indent(depth+1)<<"Argument contained free indices, not calling"<<endl;
diff --git a/environment.h b/environment.h
index d3f3031..e892207 100644
--- a/environment.h
+++ b/environment.h
@@ -21,6 +21,7 @@ private:
 	bool reduce(AST &ast,i64 depth=0);
 	bool betareduce(AST &ast,i64 depth);
 	bool resolve(AST &ast);
+	bool resolve(AST &ast,unordered_set<Name> &avoid);
 
 public:
 	void load(const Environment &other);
diff --git a/prelude.cpp b/prelude.cpp
index 5738844..8fc9d8a 100644
--- a/prelude.cpp
+++ b/prelude.cpp
@@ -17,7 +17,9 @@ const AST afterBootstrap=AST(R"RAW(
 	(def 'id \x x)
 	(def 'const \x \y x)
 	(def 'print (. putstr repr))
-	(def '$ \f \x (f x)))
+	(def '$ \f \x (f x))
+	(def 'if \c \t \f (__if c (() t) (() f)))
+	(def 'last \l (if (nil (tail l)) (head l) (last (tail l)))))
 )RAW");
 
 static AST dofunction(const AST&);
@@ -60,7 +62,11 @@ public:
 				if(arg.terms.size()==0){
 					throw FormError("Empty tuple in 'head'");
 				}
-				return arg.terms[0];
+				AST res=arg.terms[0];
+				if(arg.quoted){
+					res.quoted=true;
+				}
+				return res;
 			}));
 
 		intoEnv.define("tail",checkedHook("tail",{AST::Type::tuple},
@@ -68,7 +74,11 @@ public:
 				if(arg.terms.size()==0){
 					throw FormError("Empty tuple in 'tail'");
 				}
-				return AST::makeTuple(Terms(arg.terms.begin()+1,arg.terms.end()));
+				AST res=AST::makeTuple(Terms(arg.terms.begin()+1,arg.terms.end()));
+				if(arg.quoted){
+					res.quoted=true;
+				}
+				return res;
 			}));
 
 		intoEnv.define("nil",checkedHook("nil",{AST::Type::tuple},
@@ -81,13 +91,17 @@ public:
 				return AST::makeNumber(arg.numval==0);
 			}));
 
-		intoEnv.define("if",checkedHook("if",{AST::Type::number},{},{},
+		intoEnv.define("__if",checkedHook("__if",{AST::Type::number},{AST::Type::tuple},{AST::Type::tuple},
 			[](Environment&,const AST &arg1,const AST &arg2,const AST &arg3) -> AST {
-				if(arg1.numval!=0){
-					return arg2;
-				} else {
-					return arg3;
+				if(arg2.terms.size()!=2||arg3.terms.size()!=2){
+					throw FormError("Then and else arguments to '__if' should be 2-tuples with value in second element");
+				}
+				const AST &choice=arg1.numval!=0?arg2:arg3;
+				AST res=choice.terms[1];
+				if(choice.quoted){
+					res.quoted=true;
 				}
+				return res;
 			}));
 
 		intoEnv.define("+",checkedHook("+",{AST::Type::number,AST::Type::string},