Add Min and Max functions

Author: vanifatovvlad

README.md

@@ -71,6 +71,8 @@ Creation of custom variables is supported. Variable name may contains only engli
 | ---- | --------- | ----------- |
 | NOT  | NOT(TRUE) | Returns FALSE if argument is true, otherwise TRUE |
 | IF   | IF(n < 5, 5, n < 25, 25, 50) | Returns the second argument if the first argument is true, returns the fourth argument if the third argument is true, and so on. Otherwise, returns the last argument. Odd number of arguments required   |
+| MIN  | MIN(0, 1, ...) | Returns smallest argument |
+| MAX  | MAX(0, 1, ...) | Returns largest argument |
 
 ## How to Install
 Minimal Unity Version is 2020.1.

Runtime/ExpressionParser.cs

@@ -157,6 +157,8 @@ select MakeUnary(Negate, fact)
         private T Not(T v) => IsTrue(v) ? False : True;
         private T And(T a, T b) => IsTrue(a) ? b : a;
         private T Or(T a, T b) => IsTrue(a) ? a : b;
+        private T Min(T a, T b) => IsTrue(GreaterThan(a, b)) ? b : a;
+        private T Max(T a, T b) => IsTrue(GreaterThan(b, a)) ? b : a;
 
         private delegate Expression<T> ExprBuilder(ExpresionContext<T> context);
 
@@ -171,6 +173,12 @@ private ExprBuilder MakeFunction(string name, List<ExprBuilder> parameterBuilder
                 case "NOT":
                     return MakeFunction1(Not);
 
+                case "MIN":
+                    return MakeFunctionFold(Min);
+
+                case "MAX":
+                    return MakeFunctionFold(Max);
+
                 case "IF":
                     if (parameterBuilders.Count < 3 ||
                         parameterBuilders.Count % 2 != 1)
@@ -220,6 +228,35 @@ ExprBuilder MakeFunction1(Func<T, T> func)
                     return () => func(inner.Invoke());
                 };
             }
+
+            ExprBuilder MakeFunctionFold(Func<T, T, T> func)
+            {
+                if (parameterBuilders.Count < 1)
+                {
+                    throw new FunctionNotDefinedException(name, "Wrong parameters count");
+                }
+
+                return context =>
+                {
+                    var inner = new List<Expression<T>>();
+
+                    for (var i = 0; i < parameterBuilders.Count; i++)
+                    {
+                        inner.Add(parameterBuilders[i].Invoke(context));
+                    }
+
+                    return () =>
+                    {
+                        var result = inner[0].Invoke();
+                        for (var i = 1; i < inner.Count; i++)
+                        {
+                            result = func(result, inner[i].Invoke());
+                        }
+
+                        return result;
+                    };
+                };
+            }
         }
 
         private static ExprBuilder MakeUnary(UnaryFunc func, ExprBuilder innerBuilder)

Tests/ParserTests.cs

@@ -42,6 +42,16 @@ public class ParserTests
         [TestCase("NOT(-5)", ExpectedResult = 0)]
         [TestCase("NOT(5)", ExpectedResult = 0)]
         [TestCase("NOT(NOT(0))", ExpectedResult = 0)]
+        // MIN
+        [TestCase("MIN(0, 0)", ExpectedResult = 0)]
+        [TestCase("MIN(0, 1)", ExpectedResult = 0)]
+        [TestCase("MIN(-5, 5)", ExpectedResult = -5)]
+        [TestCase("MIN(5, 4, 7, 3, 4)", ExpectedResult = 3)]
+        // MAX
+        [TestCase("MAX(0, 0)", ExpectedResult = 0)]
+        [TestCase("MAX(0, 1)", ExpectedResult = 1)]
+        [TestCase("MAX(-5, 5)", ExpectedResult = 5)]
+        [TestCase("MAX(5, 4, 7, 3, 4)", ExpectedResult = 7)]
         // AND
         [TestCase("0 AND 0", ExpectedResult = 0)]
         [TestCase("0 AND 1", ExpectedResult = 0)]
@@ -142,6 +152,13 @@ public void Parse_Compare_Invalid()
             Assert.Throws<ParseException>(() => Compile("0 = 0 != 0", null));
         }
 
+        [Test]
+        public void Parse_MinMax_Invalid()
+        {
+            Assert.Throws<ParseException>(() => Compile("MIN()", null));
+            Assert.Throws<ParseException>(() => Compile("MAX()", null));
+        }
+
         [Test]
         public void Parse_If()
         {