Add README.md

README.md

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+## Math Executor lib by Sh18RW
+Here is a library to run as simple math expression like as `2 + 2` as `14 / (7 / (3 + (1 + (3/log(2, 4))) * 2 / 2 * 2) * (5 ^ 0 + 1))`.
+### How to use
+Library contains:
+1. Parser class.
+    ```java
+    public class App {
+        public static void main(String[] args) {
+            Parser parser = new Parser("14 / (7 / (3 + (1 + (3/log(2, 4))) * 2 / 2 * 2) * (5 ^ 0 + 1))");
+            try {
+                parser.parse();
+            } catch (ParserUnknownEntityException | ParserIllegalTokenValueException e) {
+                // process exceptions
+            }
+
+            List<Token<?>> result = parser.getResult();
+            // do something
+        }
+    }
+    ```
+    It parses an input expression to List of tokens.
+    **It doesn't check for valid sequence.**
+2. ExpressionTree class.
+    ```java
+    public class App {
+         public static void process(List<Token<?>> tokens) {
+             ExpressionsTree expressionsTree = new ExpressionsTree(tokens);
+             try {
+                 expressionsTree.build();
+             } catch (ExpressionException e) {
+                 // process exception
+             }
+
+             Expression expression = expressionsTree.getRoot();
+             // do something
+         }
+     }
+    ```
+   **Doesn't check for valid sequence at all. Only critical misspells.**
+3. Calculator class.
+    ```java
+    public class App {
+         public static void calculate(Expression expression) {
+             Calculator calculator = new Calculator();
+             double result;
+             try {
+                 result = calculator.calculate((SequenceExpression) expression);
+             } catch (CalculatorException e) {
+                 // process exception
+             }
+
+             System.out.println(result);
+         }
+     }
+    ```
+   You needn't instantiate Calculator every use, you can make it once.
+4. Number class, but I don't recommend you to use it.
+    ```java
+    public class App {
+        public static void main(String[] args) {
+            System.out.println(
+                    Numbers.getPrettierDoubleAsString(1.2345478, 4)
+                            .equals("1.2345")); // true
+            System.out.println(Numbers.countTensNumbers(11234455.01246) == 8); // true
+            System.out.println(Numbers.countNumbersAfterPoint(1.100293) == 6); // true
+            System.out.println(Numbers.equals(12.0056, 12.0040, 0.01)); // true
+            System.out.println(Numbers.lessThan(12.09, 12.0, 0.1, true)); // true
+        }
+    }
+    ```
+### Example
+```java
+package ru.corvinella;
+
+import ru.corvinella.expressions.ExpressionsTree;
+import ru.corvinella.expressions.entries.SequenceExpression;
+import ru.corvinella.expressions.exceptions.ExpressionException;
+import ru.corvinella.math.Calculator;
+import ru.corvinella.math.exceptions.CalculatorException;
+import ru.corvinella.parser.Parser;
+import ru.corvinella.parser.exceptions.ParserIllegalTokenValueException;
+import ru.corvinella.parser.exceptions.ParserUnknownEntityException;
+
+import java.util.Scanner;
+
+public class App {
+    public static void main(String[] args) throws ParserIllegalTokenValueException, ParserUnknownEntityException, ExpressionException, CalculatorException {
+        Scanner scanner = new Scanner(System.in);
+        System.out.print("Please enter an expression: ");
+
+        String expression = scanner.nextLine();
+
+        Parser parser = new Parser(expression);
+        parser.parse();
+
+        ExpressionsTree expressionsTree = new ExpressionsTree(parser.getResult());
+        expressionsTree.build();
+
+        Calculator calculator = new Calculator();
+        double result = calculator.calculate((SequenceExpression) expressionsTree.getRoot());
+
+        System.out.printf("%s = %f%n", expression, result);
+    }
+}
+```

src/test/java/ru/corvinella/CalculatorTest.java

@@ -30,7 +30,7 @@ public void testCalculator() throws ParserIllegalTokenValueException, ParserUnkn
         makeTest("2 + (2 + 2) / (2 ^ 2)", 3.0);
         makeTest("2 * (3 * (5 - log(2, 16)) / 6)", 1.0);
         makeTest("Pi*2", Math.PI*2);
-        makeTest("14 / (7 / (3 + (1 + (3/2)) * 2 / 2 * 2) * (5 ^ 0 + 1))", 8.0);
+        makeTest("14 / (7 / (3 + (1 + (3/log(2, 4))) * 2 / 2 * 2) * (5 ^ 0 + 1))", 8.0);
         makeTest("1 + 2log(2,4) / 3 - 4", 1.0 + 2.0 * 2.0 / 3.0 - 4.0);
         makeTest("3*e", 3 * Math.E);
     }