Make `last` work

1 files changed, 22 insertions, 8 deletions

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},