Ast ternary expr replaced by cond expr

Src/AST/Myc.Ast.Script.pas

@@ -50,7 +50,7 @@ var
         list_content    ::= special_form | function_call
 
         special_form    ::= "if" expression expression expression?
-                          | "?" expression expression expression
+                          | "?" (expression expression)* expression  (* cond1 branch1 ... else *)
                           | "def" identifier expression?
                           | "defmacro" identifier parameter_list expression
                           | "assign" identifier expression
@@ -206,7 +206,7 @@ type
         function VisitRecordField(const Node: IRecordFieldNode): TVoid; override;
 
         function VisitIfExpression(const Node: IIfExpressionNode): TVoid; override;
-        function VisitTernaryExpression(const Node: ITernaryExpressionNode): TVoid; override;
+        function VisitCondExpression(const Node: ICondExpressionNode): TVoid; override;
         function VisitLambdaExpression(const Node: ILambdaExpressionNode): TVoid; override;
         function VisitMacroDefinition(const Node: IMacroDefinitionNode): TVoid; override;
         function VisitQuasiquote(const Node: IQuasiquoteNode): TVoid; override;
@@ -642,9 +642,19 @@ begin
             end
             else if SameText(head.Token.Text, '?') then
             begin
-                if Length(tailNodes) <> 3 then
-                    Error('Syntax Error in ternary statement.');
-                Result := TAst.TernaryExpr(tailNodes[0], tailNodes[1], tailNodes[2], startLoc);
+                // (? test1 branch1 test2 branch2 ... else)
+                // Requires odd number of tailNodes (pairs + 1 else)
+                var count := Length(tailNodes);
+                if (count < 1) or ((count mod 2) = 0) then
+                    Error('Syntax Error: ''?'' (cond) requires an odd number of arguments (pairs of condition/branch and one final else).');
+
+                var pairs: TArray<TCondPair>;
+                SetLength(pairs, count div 2);
+                for var i := 0 to High(pairs) do
+                    pairs[i] := TCondPair.Create(tailNodes[i * 2], tailNodes[i * 2 + 1]);
+
+                var elseNode := tailNodes[High(tailNodes)];
+                Result := TAst.CondExpr(pairs, elseNode, startLoc);
             end
             else if SameText(head.Token.Text, 'def') then
             begin
@@ -946,13 +956,18 @@ begin
     Append(')');
 end;
 
-function TPrettyPrintVisitor.VisitTernaryExpression(const Node: ITernaryExpressionNode): TVoid;
+function TPrettyPrintVisitor.VisitCondExpression(const Node: ICondExpressionNode): TVoid;
 begin
-    Append('(? ');
-    Node.Condition.Accept(Self);
+    Append('(?');
     Indent;
-    NewLine;
-    Node.ThenBranch.Accept(Self);
+    for var pair in Node.Pairs do
+    begin
+        NewLine;
+        pair.Condition.Accept(Self);
+        Append(' ');
+        pair.Branch.Accept(Self);
+    end;
+    // Else
     NewLine;
     Node.ElseBranch.Accept(Self);
     Unindent;