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Embeddable expression language for Java.
There is a newer version: 1.4.4
/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2019 Twineworks GmbH
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.twineworks.tweakflow.lang.interpreter.ops;

import com.twineworks.tweakflow.lang.interpreter.EvaluationContext;
import com.twineworks.tweakflow.lang.interpreter.Interpreter;
import com.twineworks.tweakflow.lang.interpreter.Stack;
import com.twineworks.tweakflow.lang.ast.expressions.PlusNode;
import com.twineworks.tweakflow.lang.errors.LangError;
import com.twineworks.tweakflow.lang.errors.LangException;
import com.twineworks.tweakflow.lang.types.Type;
import com.twineworks.tweakflow.lang.types.Types;
import com.twineworks.tweakflow.lang.values.Value;
import com.twineworks.tweakflow.lang.values.Values;

import java.math.BigDecimal;

final public class PlusOp implements ExpressionOp {

  private final PlusNode node;
  private final ExpressionOp leftOp;
  private final ExpressionOp rightOp;

  public PlusOp(PlusNode node) {
    this.node = node;
    leftOp = node.getLeftExpression().getOp();
    rightOp = node.getRightExpression().getOp();
  }

  @Override
  public Value eval(Stack stack, EvaluationContext context) {

    Value left = leftOp.eval(stack, context);
    Value right = rightOp.eval(stack, context);

    ensureValidTypes(left, right, stack);

    if (left == Values.NIL) return Values.NIL;
    if (right == Values.NIL) return Values.NIL;

    Type leftType = left.type();
    Type rightType = right.type();

    if (leftType == Types.LONG) {
      if (rightType == Types.LONG) {
        return Values.make(left.longNum() + right.longNum());
      }
      if (rightType == Types.DOUBLE) {
        return Values.make(left.longNum() + right.doubleNum());
      }
      if (rightType == Types.DECIMAL) {
        return Values.make(BigDecimal.valueOf(left.longNum()).add(right.decimal()));
      }
    }
    if (leftType == Types.DOUBLE) {
      if (rightType == Types.LONG) {
        return Values.make(left.doubleNum() + right.longNum());
      }
      if (rightType == Types.DOUBLE) {
        return Values.make(left.doubleNum() + right.doubleNum());
      }
      if (rightType == Types.DECIMAL) {
        double d = left.doubleNum();
        if (Double.isFinite(d)) {
          return Values.make(BigDecimal.valueOf(left.doubleNum()).add(right.decimal()));
        } else {
          // NaN + some_d -> NaN
          // +-Infinity + some_d -> +-Infinity
          return left;
        }
      }
    }
    if (leftType == Types.DECIMAL) {
      if (rightType == Types.LONG) {
        return Values.make(left.decimal().add(BigDecimal.valueOf(right.longNum())));
      }
      if (rightType == Types.DOUBLE) {
        double d = right.doubleNum();
        if (Double.isFinite(d)) {
          return Values.make(left.decimal().add(BigDecimal.valueOf(d)));
        } else {
          // some_d + NaN -> NaN
          // some_d + +-Infinity -> +-Infinity
          return right;
        }

      }
      if (rightType == Types.DECIMAL) {
        return Values.make(left.decimal().add(right.decimal()));
      }
    }
    throw new LangException(LangError.CAST_ERROR, "Cannot add types: " + leftType.name() + " and " + rightType.name(), stack, node.getSourceInfo());

  }

  private void ensureValidTypes(Value left, Value right, Stack stack) {
    Type leftType = left.type();
    Type rightType = right.type();

    if ((left == Values.NIL || leftType.isNumeric()) &&
        (right == Values.NIL || rightType.isNumeric())) {
      return;
    }

    throw new LangException(LangError.CAST_ERROR, "cannot add types " + left.type().name() + " and " + right.type().name(), stack, node.getSourceInfo());

  }

  @Override
  public boolean isConstant() {
    return leftOp.isConstant() && rightOp.isConstant();
  }

  @Override
  public ExpressionOp specialize() {

    Type leftType = node.getLeftExpression().getValueType();
    Type rightType = node.getRightExpression().getValueType();

    try {

      if (leftType == rightType) {
        if (leftType == Types.DOUBLE) {
          return new PlusOpDD(node);
        }
        if (leftType == Types.LONG) {
          if (rightOp.isConstant()) {
            Value right = Interpreter.evaluateInEmptyScope(node.getRightExpression());
            if (!right.isNil()) {
              // x + non-nil const
              return new PlusOpLCL(node);
            }
          }
          return new PlusOpLL(node);
        }
        if (leftType == Types.DECIMAL) {
          return new PlusOpDecDec(node);
        }
      }
    } catch (LangException ignored) {
    }

    return new PlusOp(node);
  }

  @Override
  public ExpressionOp refresh() {
    return new PlusOp(node);
  }


}