September 2017 Update
This commit is contained in:
Ingy döt Net
parent
bba7bfd280
commit
ba8067c3b7
14570 changed files with 153136 additions and 63871 deletions
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@ -1,138 +1,165 @@
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import java.util.Stack;
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public class ArithmeticEvaluation
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{
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public static enum Parentheses { LEFT, RIGHT }
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public class ArithmeticEvaluation {
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public static enum BinaryOperator
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{
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ADD('+', 1) {
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public BigRational eval(BigRational leftValue, BigRational rightValue) { return leftValue.add(rightValue); }
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},
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SUB('-', 1) {
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public BigRational eval(BigRational leftValue, BigRational rightValue) { return leftValue.subtract(rightValue); }
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},
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MUL('*', 2) {
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public BigRational eval(BigRational leftValue, BigRational rightValue) { return leftValue.multiply(rightValue); }
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},
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DIV('/', 2) {
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public BigRational eval(BigRational leftValue, BigRational rightValue) { return leftValue.divide(rightValue); }
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};
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public final char symbol;
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public final int precedence;
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BinaryOperator(char symbol, int precedence)
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{
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this.symbol = symbol;
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this.precedence = precedence;
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public interface Expression {
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BigRational eval();
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}
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public abstract BigRational eval(BigRational leftValue, BigRational rightValue);
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}
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public enum Parentheses {LEFT}
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public static class BinaryExpression
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{
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public Object leftOperand = null;
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public BinaryOperator operator = null;
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public Object rightOperand = null;
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public enum BinaryOperator {
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ADD('+', 1),
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SUB('-', 1),
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MUL('*', 2),
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DIV('/', 2);
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public BinaryExpression(Object leftOperand, BinaryOperator operator, Object rightOperand)
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{
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this.leftOperand = leftOperand;
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this.operator = operator;
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this.rightOperand = rightOperand;
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}
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public final char symbol;
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public final int precedence;
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public BigRational eval()
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{
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BigRational leftValue = (leftOperand instanceof BinaryExpression) ? ((BinaryExpression)leftOperand).eval() : (BigRational)leftOperand;
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BigRational rightValue = (rightOperand instanceof BinaryExpression) ? ((BinaryExpression)rightOperand).eval() : (BigRational)rightOperand;
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return operator.eval(leftValue, rightValue);
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}
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public String toString()
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{ return "(" + leftOperand + " " + operator.symbol + " " + rightOperand + ")"; }
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}
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public static void createNewOperand(BinaryOperator operator, Stack<Object> operands)
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{
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Object rightOperand = operands.pop();
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operands.push(new BinaryExpression(operands.pop(), operator, rightOperand));
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return;
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}
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public static Object createExpression(String inputString)
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{
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int curIndex = 0;
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boolean afterOperand = false;
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Stack<Object> operands = new Stack<Object>();
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Stack<Object> operators = new Stack<Object>();
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inputStringLoop:
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while (curIndex < inputString.length())
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{
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int startIndex = curIndex;
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char c = inputString.charAt(curIndex++);
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if (Character.isWhitespace(c))
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continue;
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if (afterOperand)
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{
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if (c == ')')
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{
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Object operator = null;
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while (!operators.isEmpty() && ((operator = operators.pop()) != Parentheses.LEFT))
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createNewOperand((BinaryOperator)operator, operands);
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continue;
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BinaryOperator(char symbol, int precedence) {
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this.symbol = symbol;
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this.precedence = precedence;
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}
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afterOperand = false;
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for (BinaryOperator operator : BinaryOperator.values())
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{
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if (c == operator.symbol)
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{
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while (!operators.isEmpty() && (operators.peek() != Parentheses.LEFT) && (((BinaryOperator)operators.peek()).precedence >= operator.precedence))
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createNewOperand((BinaryOperator)operators.pop(), operands);
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operators.push(operator);
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continue inputStringLoop;
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}
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public BigRational eval(BigRational leftValue, BigRational rightValue) {
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switch (this) {
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case ADD:
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return leftValue.add(rightValue);
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case SUB:
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return leftValue.subtract(rightValue);
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case MUL:
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return leftValue.multiply(rightValue);
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case DIV:
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return leftValue.divide(rightValue);
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}
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throw new IllegalStateException();
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}
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public static BinaryOperator forSymbol(char symbol) {
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for (BinaryOperator operator : values()) {
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if (operator.symbol == symbol) {
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return operator;
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}
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}
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throw new IllegalArgumentException(String.valueOf(symbol));
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}
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throw new IllegalArgumentException();
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}
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if (c == '(')
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{
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operators.push(Parentheses.LEFT);
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continue;
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}
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afterOperand = true;
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while (curIndex < inputString.length())
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{
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c = inputString.charAt(curIndex);
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if (((c < '0') || (c > '9')) && (c != '.'))
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break;
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curIndex++;
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}
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operands.push(BigRational.valueOf(inputString.substring(startIndex, curIndex)));
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}
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while (!operators.isEmpty())
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{
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Object operator = operators.pop();
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if (operator == Parentheses.LEFT)
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throw new IllegalArgumentException();
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createNewOperand((BinaryOperator)operator, operands);
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}
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Object expression = operands.pop();
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if (!operands.isEmpty())
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throw new IllegalArgumentException();
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return expression;
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}
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public static class Number implements Expression {
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private final BigRational number;
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public static void main(String[] args)
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{
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String[] testExpressions = { "2+3", "2+3/4", "2*3-4", "2*(3+4)+5/6", "2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10", "2*-3--4+-.25" };
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for (String testExpression : testExpressions)
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{
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Object expression = createExpression(testExpression);
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System.out.println("Input: \"" + testExpression + "\", AST: \"" + expression + "\", eval=" + (expression instanceof BinaryExpression ? ((BinaryExpression)expression).eval() : expression));
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public Number(BigRational number) {
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this.number = number;
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}
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@Override
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public BigRational eval() {
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return number;
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}
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@Override
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public String toString() {
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return number.toString();
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}
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}
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public static class BinaryExpression implements Expression {
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public final Expression leftOperand;
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public final BinaryOperator operator;
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public final Expression rightOperand;
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public BinaryExpression(Expression leftOperand, BinaryOperator operator, Expression rightOperand) {
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this.leftOperand = leftOperand;
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this.operator = operator;
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this.rightOperand = rightOperand;
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}
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@Override
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public BigRational eval() {
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BigRational leftValue = leftOperand.eval();
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BigRational rightValue = rightOperand.eval();
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return operator.eval(leftValue, rightValue);
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}
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@Override
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public String toString() {
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return "(" + leftOperand + " " + operator.symbol + " " + rightOperand + ")";
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}
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}
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private static void createNewOperand(BinaryOperator operator, Stack<Expression> operands) {
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Expression rightOperand = operands.pop();
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Expression leftOperand = operands.pop();
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operands.push(new BinaryExpression(leftOperand, operator, rightOperand));
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}
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public static Expression parse(String input) {
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int curIndex = 0;
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boolean afterOperand = false;
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Stack<Expression> operands = new Stack<>();
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Stack<Object> operators = new Stack<>();
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while (curIndex < input.length()) {
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int startIndex = curIndex;
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char c = input.charAt(curIndex++);
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if (Character.isWhitespace(c))
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continue;
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if (afterOperand) {
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if (c == ')') {
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Object operator;
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while (!operators.isEmpty() && ((operator = operators.pop()) != Parentheses.LEFT))
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createNewOperand((BinaryOperator) operator, operands);
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continue;
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}
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afterOperand = false;
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BinaryOperator operator = BinaryOperator.forSymbol(c);
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while (!operators.isEmpty() && (operators.peek() != Parentheses.LEFT) && (((BinaryOperator) operators.peek()).precedence >= operator.precedence))
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createNewOperand((BinaryOperator) operators.pop(), operands);
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operators.push(operator);
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continue;
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}
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if (c == '(') {
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operators.push(Parentheses.LEFT);
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continue;
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}
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afterOperand = true;
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while (curIndex < input.length()) {
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c = input.charAt(curIndex);
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if (((c < '0') || (c > '9')) && (c != '.'))
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break;
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curIndex++;
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}
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operands.push(new Number(BigRational.valueOf(input.substring(startIndex, curIndex))));
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}
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while (!operators.isEmpty()) {
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Object operator = operators.pop();
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if (operator == Parentheses.LEFT)
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throw new IllegalArgumentException();
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createNewOperand((BinaryOperator) operator, operands);
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}
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Expression expression = operands.pop();
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if (!operands.isEmpty())
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throw new IllegalArgumentException();
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return expression;
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}
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public static void main(String[] args) {
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String[] testExpressions = {
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"2+3",
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"2+3/4",
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"2*3-4",
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"2*(3+4)+5/6",
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"2 * (3 + (4 * 5 + (6 * 7) * 8) - 9) * 10",
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"2*-3--4+-.25"};
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for (String testExpression : testExpressions) {
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Expression expression = parse(testExpression);
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System.out.printf("Input: \"%s\", AST: \"%s\", value=%s%n", testExpression, expression, expression.eval());
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}
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}
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}
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}
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