Rework for loops to use iterators, requiring pairs or ipairs function to handle multi-assignment

Upsilon/BaseTypes/ScriptIterator.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using Upsilon.BaseTypes.ScriptTypeInterfaces;
+
+namespace Upsilon.BaseTypes
+{
+    internal abstract class ScriptIterator : ScriptType, IIterable
+    {
+        public IIterable BaseIterator { get; }
+        public override Type Type => Type.Table;
+
+        public ScriptIterator(IIterable baseIterator)
+        {
+            BaseIterator = baseIterator;
+        }
+
+        public override object ToCSharpObject()
+        {
+            return GetEnumerator();
+        }
+
+        public override System.Type GetCSharpType()
+        {
+            return typeof(IEnumerator<ScriptType>);
+        }
+
+        public ScriptType GetValueFromIndex(ScriptType index)
+        {
+            throw new InvalidOperationException();
+        }
+
+        public abstract IEnumerator<ScriptType> GetEnumerator();
+
+    }
+
+    internal class UpTillNullPairsScriptIterator : ScriptIterator
+    {
+        public UpTillNullPairsScriptIterator(IIterable baseIterator) : base(baseIterator)
+        {
+        }
+
+        public override IEnumerator<ScriptType> GetEnumerator()
+        {
+            using(var baseEnumerator = BaseIterator.GetEnumerator())
+            {
+                while (baseEnumerator.MoveNext())
+                {
+                    var key = baseEnumerator.Current;
+                    if (key == null)
+                        break;
+                    var value = BaseIterator.GetValueFromIndex(key);
+                    if (value == null)
+                        break;
+                    yield return new SimpleScriptTable(new List<ScriptType>(){key, value});
+                }
+            }
+        }
+    }
+
+    internal class PairsScriptIterator : ScriptIterator
+    {
+        public PairsScriptIterator(IIterable baseIterator) : base(baseIterator)
+        {
+        }
+
+        public override IEnumerator<ScriptType> GetEnumerator()
+        {
+            using(var baseEnumerator = BaseIterator.GetEnumerator())
+            {
+                while (baseEnumerator.MoveNext())
+                {
+                    var key = baseEnumerator.Current;
+                    var value = BaseIterator.GetValueFromIndex(key);
+                    yield return new SimpleScriptTable(new List<ScriptType>(){key, value});
+                }
+            }
+        }
+    }
+
+}

Upsilon/BaseTypes/ScriptTable.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using Upsilon.BaseTypes.ScriptTypeInterfaces;
@@ -44,16 +45,25 @@ namespace Upsilon.BaseTypes
             EvaluationScope.CreateLocal(new VariableSymbol(s, value.Type, false), value);
         }
 
-        public IEnumerator<(string Key, ScriptType value)> GetEnumerator()
+        public ScriptType GetValueFromIndex(ScriptType index)
+        {
+            if (EvaluationScope.TryGet(index.ToString(), out var result))
+            {
+                return result;
+            }
+            throw new Exception($"Can't find key '{index}' in table.");
+        }
+
+        public IEnumerator<ScriptType> GetEnumerator()
         {
             return Enumerator();
         }
 
-        private IEnumerator<(string Key, ScriptType value)> Enumerator()
+        private IEnumerator<ScriptType> Enumerator()
         {
             foreach (var variable in EvaluationScope.Variables)
             {
-                yield return (variable.Key, variable.Value);
+                yield return variable.Key.ToScriptType();
             }
         }
     }

Upsilon/BaseTypes/ScriptTypeInterfaces/IITerable.cs

@@ -1,9 +1,11 @@
 using System.Collections.Generic;
+using Upsilon.Evaluator;
 
 namespace Upsilon.BaseTypes.ScriptTypeInterfaces
 {
     internal interface IIterable
     {
-        IEnumerator<(string Key, ScriptType value)> GetEnumerator();
+        ScriptType GetValueFromIndex(ScriptType index);
+        IEnumerator<ScriptType> GetEnumerator();
     }
 }

Upsilon/BaseTypes/SimpleScriptTable.cs

@@ -38,6 +38,8 @@ namespace Upsilon.BaseTypes
             return _objects[i];
         }
 
+        public ScriptType this[int index] => _objects[index];
+
         public void Set(Diagnostics diagnostics, TextSpan span, ScriptType index, ScriptType value)
         {
             throw new System.NotImplementedException();

Upsilon/BaseTypes/UserData/ListUserData.cs

@@ -1,5 +1,7 @@
+using System;
 using System.Collections;
 using System.Collections.Generic;
+using Upsilon.BaseTypes.Number;
 using Upsilon.BaseTypes.ScriptTypeInterfaces;
 using Upsilon.Evaluator;
 using Upsilon.Text;
@@ -51,9 +53,18 @@ namespace Upsilon.BaseTypes.UserData
             return List.GetType();
         }
 
-        public IEnumerator<(string Key, ScriptType value)> GetEnumerator()
+        public ScriptType GetValueFromIndex(ScriptType index)
         {
-            throw new System.NotImplementedException();
+            var num = (ScriptNumberLong)index;
+            return List[(int) num.Value].ToScriptType();
+        }
+
+        public IEnumerator<ScriptType> GetEnumerator()
+        {
+            for (int i = 0; i < List.Count; i++)
+            {
+                yield return new ScriptNumberLong(i);
+            }
         }
     }
 }

Upsilon/Evaluator/Evaluator.cs

@@ -548,11 +548,17 @@ namespace Upsilon.Evaluator
             {
                 while (enumerator.MoveNext())
                 {
-                    var (key, value) = enumerator.Current;
+                    var current = enumerator.Current;
+                    if (current == null || current.Type != Type.Table)
+                    {
+                        throw new Exception($"Can't assign result value with type '{current.Type}' to multiple values");
+                    }
+
+                    var table = (SimpleScriptTable)current;
                     if (e.Variables[0].Name != "_")
-                        innerEvaluator.Scope.CreateLocal(e.Variables[0], key.ToScriptType());
+                        innerEvaluator.Scope.CreateLocal(e.Variables[0], table[0].ToScriptType());
                     if (e.Variables[1].Name != "_")
-                        innerEvaluator.Scope.CreateLocal(e.Variables[1], value);
+                        innerEvaluator.Scope.CreateLocal(e.Variables[1], table[1]);
                     innerEvaluator.EvaluateBoundBlockStatement((BoundBlockStatement) e.Block);
                     if (innerEvaluator.HasBroken)
                         break;

Upsilon/StandardLibraries/BasicFunctions.cs

@@ -1,9 +1,7 @@
 using System;
-using System.Collections.Generic;
 using Upsilon.BaseTypes;
 using Upsilon.BaseTypes.Number;
 using Upsilon.BaseTypes.ScriptTypeInterfaces;
-using Type = Upsilon.BaseTypes.Type;
 
 // ReSharper disable UnusedMember.Global
 // ReSharper disable MemberCanBePrivate.Global
@@ -28,11 +26,18 @@ namespace Upsilon.StandardLibraries
         }
 
         [StandardLibraryScriptFunction("ipairs")]
+        public IIterable UpTillNullPairs(IIterable table)
+        {
+            return new UpTillNullPairsScriptIterator(table);
+        }
+
+        [StandardLibraryScriptFunction("pairs")]
         public IIterable Pairs(IIterable table)
         {
-            return table;
+            return new PairsScriptIterator(table);
         }
 
+
         [StandardLibraryScriptFunction("tonumber")]
         public ScriptNumber ToNumber(ScriptString obj)
         {

UpsilonTests/GeneralTests/ForLoopTests.cs

@@ -85,7 +85,7 @@ return a
             const string input = @"
 arr = {100, 56, 28}
 value = 0
-for key, val in arr do
+for key, val in ipairs(arr) do
     value = value + val
 end
 return value
@@ -103,7 +103,7 @@ return value
             const string input = @"
 arr = {100, 56, 28}
 value = 0
-for key, val in arr do
+for key, val in ipairs(arr) do
     local keyInt = tonumber(key)
     value = value + keyInt
 end

UpsilonTests/GeneralTests/FunctionTests.cs

@@ -206,7 +206,7 @@ end
             const string input = @"
 arr = {100, 56, 28}
 value = 0
-for key, val in arr do
+for key, val in ipairs(arr) do
     value = value + tonumber(key)
 end
 return value

UpsilonTests/GeneralTests/ScopeTests.cs

@@ -51,7 +51,7 @@ b = a
             const string input = @"
 arr = {100, 56, 28}
 local value = 0
-for key, val in arr do
+for key, val in ipairs(arr) do
     value = value + val
 end
 return value