add if/then/else functions

szensk · Nov 21, 2017 · 15b5066 · 15b5066
1 parent 3c7e53b
commit 15b5066
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Showing 12 changed files with 103 additions and 36 deletions.
diff --git a/Wul/Interpreter/Bool.cs b/Wul/Interpreter/Bool.cs
@@ -2,8 +2,8 @@
 {
     class Bool : IValue
     {
-        public static Bool True => new Bool(true);
-        public static Bool False => new Bool(false);
+        public static Bool True = new Bool(true);
+        public static Bool False = new Bool(false);
 
         public readonly bool Value;
 

diff --git a/Wul/Interpreter/Function.cs b/Wul/Interpreter/Function.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using Wul.Parser;
 
 namespace Wul.Interpreter
@@ -27,12 +28,15 @@ public IValue Evaluate(List<IValue> arguments, Scope scope)
             {
                 string argName = ArgumentNames[i];
                 currentScope[argName] = arguments[i];
+                Debug.WriteLine($"Binding {argName} = {arguments[i].AsString()}");
             }
 
-            return WulInterpreter.Interpret(Body, currentScope);
+            IValue result = WulInterpreter.Interpret(Body, currentScope);
+            Debug.WriteLine($"Returning {result.AsString()}");
+            return result;
         }
 
-        public virtual void Execute(ListNode list, Scope scope)
+        public virtual IValue Execute(ListNode list, Scope scope)
         {
             throw new NotImplementedException();
         }
@@ -62,7 +66,7 @@ public IValue Evaluate(List<IValue> arguments, Scope scope)
             return Body(arguments, scope);
         }
 
-        public virtual void Execute(ListNode list, Scope scope)
+        public virtual IValue Execute(ListNode list, Scope scope)
         {
             throw new NotImplementedException();
         }
@@ -91,9 +95,9 @@ public IValue Evaluate(List<IValue> arguments, Scope scope)
             throw new NotImplementedException();
         }
 
-        public virtual void Execute(ListNode list, Scope scope)
+        public virtual IValue Execute(ListNode list, Scope scope)
         {
-            Body(list, scope);
+            return Body(list, scope);
         }
 
         public string AsString()

diff --git a/Wul/Interpreter/GlobalScope.cs b/Wul/Interpreter/GlobalScope.cs
@@ -17,6 +17,12 @@ public static void RegisterDefaultFunctions()
 
                 //Comparison
                 Scope["="] = StdLib.Comparison.Equal;
+                Scope["<"] = StdLib.Comparison.LessThan;
+
+                //Conditional
+                Scope["if"] = StdLib.General.If;
+                Scope["then"] = StdLib.General.Then;
+                Scope["else"] = StdLib.General.Then; //Not a typo!
 
                 //Bools
                 Scope["true"] = Bool.True;
@@ -29,7 +35,7 @@ public static void RegisterDefaultFunctions()
                 //Arith
                 Scope["+"] = StdLib.Arithmetic.Add;
                 Scope["-"] = StdLib.Arithmetic.Subtract;
-                Scope["<"] = StdLib.Arithmetic.LessThan;
+                Scope["*"] = StdLib.Arithmetic.Multiply;
             }
         }
     }

diff --git a/Wul/Interpreter/IFunction.cs b/Wul/Interpreter/IFunction.cs
@@ -8,6 +8,6 @@ interface IFunction : IValue
         string Name { get; }
         List<string> ArgumentNames { get; }
         IValue Evaluate(List<IValue> arguments, Scope scope);
-        void Execute(ListNode list, Scope scope);
+        IValue Execute(ListNode list, Scope scope);
     }
 }
diff --git a/Wul/Interpreter/ListTable.cs b/Wul/Interpreter/ListTable.cs
@@ -56,6 +56,11 @@ public override void Assign(IValue key, IValue value)
 
         public override Number Count => _list.Count;
 
+        public override string AsString()
+        {
+            return "(" + string.Join(", ", _list.Select(s => s.AsString()).ToList()) + ")";
+        }
+
         public override IValue this[IValue key]
         {
             get => Get(key);

diff --git a/Wul/Interpreter/Table.cs b/Wul/Interpreter/Table.cs
@@ -12,7 +12,7 @@ abstract class Table : IValue
 
         public abstract Number Count { get; }
 
-        public string AsString()
+        public virtual string AsString()
         {
             return $"List[{Count.Value}]";
         }

diff --git a/Wul/Interpreter/WulInterpreter.cs b/Wul/Interpreter/WulInterpreter.cs
@@ -81,7 +81,7 @@ private static IValue Evaluate(ListNode list, Scope currentScope = null)
             } 
             else if (first is ListNode)
             {
-                value = Evaluate((ListNode) first);
+                value = Evaluate((ListNode) first, currentScope);
             }
 
             IFunction function = value as IFunction;
@@ -96,14 +96,20 @@ private static IValue Evaluate(ListNode list, Scope currentScope = null)
             {
                 //Invoke a magic function
                 //Magic functions do not have their arguments evaluated, it's up the function to do so
-                magicFunction.Execute(list, currentScope);
-                value = Value.Nil;
+                value = magicFunction.Execute(list, currentScope);
             }
             else
             {
                 //Evaluate a list
                 var remaining = list.Children.Select(node => Interpret(node, currentScope)).ToArray();
-                value = new ListTable(remaining);
+                if (remaining.Length > 1)
+                {
+                    value = new ListTable(remaining);
+                }
+                else if (remaining.Length == 1)
+                {
+                    value = remaining[0];
+                }
             }
 
             return value;

diff --git a/Wul/Parser/List.cs b/Wul/Parser/List.cs
@@ -32,27 +32,27 @@ public override SyntaxNode Parse(string token)
             List<SyntaxNode> children = new List<SyntaxNode>();
 
             int currentIndex = 0;
-            int openParenthesis = 0;
-            int closeParenthesis = 0;
+            int openParentheses = 0;
+            int closeParentheses = 0;
             int startIndex = 0;
             while (currentIndex < inner.Length)
             {
                 if (inner[currentIndex] == '(')
                 {
-                    openParenthesis++;
+                    openParentheses++;
                 }
                 else if (inner[currentIndex] == ')')
                 {
-                    closeParenthesis++;
+                    closeParentheses++;
                 }
 
-                if (closeParenthesis > openParenthesis)
+                if (closeParentheses > openParentheses)
                 {
                     throw new Exception("Mismatched parenthesis, have fun");
                 }
 
                 currentIndex++;
-                if ((currentIndex == inner.Length || inner[currentIndex] == ' ' || inner[currentIndex] == ')') && openParenthesis == closeParenthesis)
+                if ((currentIndex == inner.Length || inner[currentIndex] == ' ' || inner[currentIndex] == ')') && openParentheses == closeParentheses)
                 {
                     string currentInner = inner.Substring(startIndex, currentIndex - startIndex);
                     var item = Parse(currentInner) ?? identifierParser.Parse(currentInner) ?? numericParser.Parse(currentInner);

diff --git a/Wul/StdLib/Arithmetic.cs b/Wul/StdLib/Arithmetic.cs
@@ -16,20 +16,6 @@ internal class Arithmetic
             return (Number) sum;
         }, "+");
 
-        internal static IFunction LessThan = new NetFunction((list, scope) =>
-        {
-            var first = list.First() as Number;
-            var second = list.Skip(1).First() as Number;
-            if (first.Value < second.Value)
-            {
-                return (Number) 1;
-            }
-            else
-            {
-                return (Number) 0;
-            }
-        }, "<");
-
         internal static IFunction Subtract = new NetFunction((list, scope) =>
         {
             var first = list.First() as Number;
@@ -40,6 +26,21 @@ internal class Arithmetic
             }
             double sum = numbers.Sum(x => x.Value);
             return (Number) (first.Value - sum);
-        }, "+");
+        }, "-");
+
+        internal static IFunction Multiply = new NetFunction((list, scope) =>
+        {
+            var numbers = list.Select(x => x as Number).Where(x => x != null).ToArray();
+            if (!numbers.Any())
+            {
+                return Value.Nil;
+            }
+            double multiplied = numbers[0];
+            for (int i = 1; i < numbers.Length; ++i)
+            {
+                multiplied *= numbers[i];
+            }
+            return (Number)multiplied;
+        }, "*");
     }
 }
diff --git a/Wul/StdLib/Comparison.cs b/Wul/StdLib/Comparison.cs
@@ -12,5 +12,14 @@ internal class Comparison
             bool equal = first.Equals(second);
             return equal ? Bool.True : Bool.False;
         }, "=");
+
+        internal static IFunction LessThan = new NetFunction((list, scope) =>
+        {
+            Number first = list[0] as Number;
+            Number second = list[1] as Number;
+            //TODO make all IValue override Equals
+            bool lessThan = first.Value < second.Value;
+            return lessThan ? Bool.True : Bool.False;
+        }, "<");
     }
 }
diff --git a/Wul/StdLib/General.cs b/Wul/StdLib/General.cs
@@ -33,5 +33,41 @@ class General
 
             return function;
         }, "def");
+
+        internal static IFunction Then = new NetFunction((list, scope) =>
+        {
+            if (list.Count == 1)
+            {
+                return list.First();
+            }
+            else
+            {
+                return new ListTable(list.ToArray());
+            }
+        }, "then/else");
+
+        internal static IFunction If = new MagicNetFunction((list, scope) =>
+        {
+            var children = list.Children.Skip(1).ToArray();
+
+            var condition = children[0];
+            var result = WulInterpreter.Interpret(condition, scope);
+
+            var listChildren = children.OfType<ListNode>();
+
+            IValue returnValue = Value.Nil;
+            if (result != Value.Nil && result != Bool.False)
+            {
+                var thenBlock = listChildren.FirstOrDefault(l => (l.Children.First() as IdentifierNode)?.Name == "then");
+                returnValue = WulInterpreter.Interpret(thenBlock, scope);
+            }
+            else
+            {
+                var elseBlock = listChildren.FirstOrDefault(l => (l.Children.First() as IdentifierNode)?.Name == "else");
+                returnValue = WulInterpreter.Interpret(elseBlock, scope);
+            }
+
+            return returnValue;
+        }, "if");
     }
 }
diff --git a/Wul/Wul.cs b/Wul/Wul.cs
@@ -11,7 +11,7 @@ class Wul
     {
         static void Main(string[] args)
         {
-            //built ins: def, if, -, <, then, else
+            //built ins: if, then, else
             var parser = new ProgramParser();
             Global.RegisterDefaultFunctions();