From 3c04f617ac5d6722c7567c2a8169c80982e01a6b Mon Sep 17 00:00:00 2001
From: sys_27 <sys2712@gmail.com>
Date: Sat, 17 Oct 2015 21:01:03 +0300
Subject: [PATCH] Added #106

---
 xFunc.Maths/Lexer.cs         | 22 ++++++++++++++++------
 xFunc.Tests/MathLexerTest.cs | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/xFunc.Maths/Lexer.cs b/xFunc.Maths/Lexer.cs
index 22bb4a4ed..53c0c8648 100644
--- a/xFunc.Maths/Lexer.cs
+++ b/xFunc.Maths/Lexer.cs
@@ -368,12 +368,12 @@ public IEnumerable<IToken> Tokenize(string function)
                     if (letter == '0' && i + 1 < function.Length)
                     {
                         var nextLetter = function[i + 1];
-                        if (nextLetter == 'x' && i + 2 < function.Length)
+                        if (nextLetter == 'x' && i + 2 < function.Length) // hex
                         {
                             i += 2;
 
                             length = 1;
-                            for (j = i + 1; j < function.Length && (char.IsDigit(function[j]) || (function[j] >= 97 && function[j] <= 102)); j++)
+                            for (j = i + 1; j < function.Length && (char.IsDigit(function[j]) || (function[j] >= 97 && function[j] <= 102)); j++) // from 'a' to 'f'
                                 length++;
 
                             strNumber = function.Substring(i, length);
@@ -383,7 +383,7 @@ public IEnumerable<IToken> Tokenize(string function)
                             i += length;
                             continue;
                         }
-                        if (nextLetter == 'b' && i + 2 < function.Length)
+                        if (nextLetter == 'b' && i + 2 < function.Length) // bin
                         {
                             i += 2;
 
@@ -398,7 +398,7 @@ public IEnumerable<IToken> Tokenize(string function)
                             i += length;
                             continue;
                         }
-                        if (char.IsDigit(nextLetter))
+                        if (char.IsDigit(nextLetter)) // oct
                         {
                             length = 1;
                             for (j = i + 1; j < function.Length && char.IsDigit(function[j]); j++)
@@ -413,6 +413,8 @@ public IEnumerable<IToken> Tokenize(string function)
                         }
                     }
 
+                    // normal number (dec)
+
                     length = 1;
                     for (j = i + 1; j < function.Length && char.IsDigit(function[j]); j++)
                         length++;
@@ -424,6 +426,16 @@ public IEnumerable<IToken> Tokenize(string function)
                             length++;
                     }
 
+                    if (CheckNextSymbol(function, i + length - 1, 'e')) // exp notation
+                    {
+                        length++;
+                        if (CheckNextSymbol(function, i + length - 1, '-'))
+                            length++;
+
+                        for (j = i + length; j < function.Length && char.IsDigit(function[j]); j++)
+                            length++;
+                    }
+
                     strNumber = function.Substring(i, length);
                     number = double.Parse(strNumber, CultureInfo.InvariantCulture);
                     tokens.Add(new NumberToken(number));
@@ -432,9 +444,7 @@ public IEnumerable<IToken> Tokenize(string function)
 
                     var f = function.Substring(i);
                     if (i < function.Length && char.IsLetter(function[i]) && !notVar.Any(f.StartsWith))
-                    {
                         tokens.Add(new OperationToken(Operations.Multiplication));
-                    }
 
                     continue;
                 }
diff --git a/xFunc.Tests/MathLexerTest.cs b/xFunc.Tests/MathLexerTest.cs
index 13ba6f796..a2c208685 100644
--- a/xFunc.Tests/MathLexerTest.cs
+++ b/xFunc.Tests/MathLexerTest.cs
@@ -72,6 +72,41 @@ public void Brackets()
             Assert.Equal(expected, tokens.ToList());
         }
 
+        [Fact]
+        public void ExpNumber1()
+        {
+            var tokens = lexer.Tokenize("1.2345E-10");
+            var expected = new List<IToken>
+            {
+                new NumberToken(0.00000000012345)
+            };
+            Assert.Equal(expected, tokens.ToList());
+        }
+
+        [Fact]
+        public void ExpNumber2()
+        {
+            var tokens = lexer.Tokenize("1.2345E10");
+            var expected = new List<IToken>
+            {
+                new NumberToken(12345000000)
+            };
+            Assert.Equal(expected, tokens.ToList());
+        }
+        
+        [Fact]
+        public void ExpNumber3()
+        {
+            var tokens = lexer.Tokenize("1.2e2 + 2.1e-3");
+            var expected = new List<IToken>
+            {
+                new NumberToken(120),
+                new OperationToken(Operations.Addition),
+                new NumberToken(0.0021)
+            };
+            Assert.Equal(expected, tokens.ToList());
+        }
+
         [Fact]
         public void Add()
         {