Distribute.java :  » Algebra » symja » org » matheclipse » core » reflection » system » Java Open Source

package org.matheclipse.core.reflection.system;

import org.matheclipse.core.eval.exception.Validate;
import org.matheclipse.core.eval.interfaces.AbstractFunctionEvaluator;
import org.matheclipse.core.expression.F;
import org.matheclipse.core.interfaces.IAST;
import org.matheclipse.core.interfaces.IExpr;

/**
 *  
 */
public class Distribute extends AbstractFunctionEvaluator {

  public Distribute() {
  }

  @Override
  public IExpr evaluate(final IAST ast) {
    Validate.checkRange(ast, 2, 4);

    IExpr arg1 = ast.get(1);
    IExpr head = F.Plus;
    if (ast.size() >= 3) {
      head = ast.get(2);
    }
    if (ast.size() == 4) {
      if (!arg1.head().equals(ast.get(3))) {
        return arg1;
      }
    }

    if (arg1.isAST()) {
      IAST resultCollector = F.ast(head);
      IAST stepResult = F.ast(arg1.head());
      distributePosition(resultCollector, stepResult, head, (IAST) arg1, 1);
      return resultCollector;
    }
    return arg1;
  }

  private void distributePosition(IAST resultCollector, IAST stepResult, IExpr head, IAST arg1, int position) {
    if (arg1.size() == position) {
      resultCollector.add(stepResult);
      return;
    }
    if (arg1.size() < position) {
      return;
    }
    if (arg1.get(position).head().equals(head) && arg1.get(position).isAST()) {
      IAST temp = (IAST) arg1.get(position);
      for (int i = 1; i < temp.size(); i++) {
        IAST res2 = stepResult.clone();
        res2.add(temp.get(i));
        distributePosition(resultCollector, res2, head, (IAST) arg1, position + 1);
      }
    } else {
      IAST res2 = stepResult.clone();
      res2.add(arg1.get(position));
      distributePosition(resultCollector, res2, head, (IAST) arg1, position + 1);
    }

  }
}