Allow identifiers to contain numbers and underscores, however numbers may not be the first character of the identifier

Updated test cases to test this

source/tlang/compiler/parser.d

@@ -414,6 +414,12 @@ public final class Parser
     }
 
     /* Almost like parseBody but has more */
+    /**
+    * TODO: For certain things like `parseClass` we should
+    * keep track of what level we are at as we shouldn't allow
+    * one to define classes within functions
+    */
+    /* TODO: Variables should be allowed to have letters in them and underscores */
     public void parse()
     {
         /* TODO: Do parsing here */

source/tlang/compiler/symbols.d

@@ -66,17 +66,53 @@ public static bool isType(string tokenStr)
                 "long") == 0 || cmp(tokenStr, "ulong") == 0 || cmp(tokenStr, "void") == 0;
 }
 
-private static bool isAlpha(string token)
+/**
+* Checks if the given character is a letter
+*/
+private static bool isCharacterAlpha(char character)
 {
+    return (character >= 65 && character <= 90) || (character >= 97 && character <= 122);
+}
+
+/**
+* Checks if the given character is a number
+*/
+private static bool isCharacterNumber(char character)
+{
+    return (character >= 48 && character <= 57);
+}
+
+private static bool isIdentifier(string token)
+{
+    /* This is used to prevent the first character from not being number */
+    bool isFirstRun = true;
+
     foreach (char character; token)
     {
-        if ((character >= 65 && character <= 90) || (character >= 97 && character <= 122))
+        if(isFirstRun)
         {
+            /* Only allow underscore of letter */
+            if(isCharacterAlpha(character) || character == '_')
+            {
 
+            }
+            else
+            {
+                return false;
+            }
+
+            isFirstRun = false;
         }
         else
         {
-            return false;
+            if(isCharacterAlpha(character) || character == '_' || isCharacterNumber(character))
+            {
+
+            }
+            else
+            {
+                return false;
+            }
         }
     }
 
@@ -193,12 +229,8 @@ public static SymbolType getSymbolType(Token tokenIn)
     {
         return SymbolType.DELETE;
     }
-    
-    
-    
-    
     /* Identifier check (TODO: Track vars) */
-    else if (isAlpha(token))
+    else if (isIdentifier(token))
     {
         return SymbolType.IDENTIFIER;
     }

source/tlang/testing/basic1.t

@@ -3,14 +3,14 @@ ubyte y;
 
 ubyte k = 1;
 
-class clazzOne
+class clazz1
 {
     print("Hello world");
 }
 
-class clazzTwo
+class clazz_2_1
 {
-
+    
 }