Android Open Source - bin.calc_android Exp Parser

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License

The source code is released under:

GNU General Public License

Java Source Code

package info.ohgita.android.bincalc.calculator;
/*from   w ww . j  ava 2 s.com*/
import java.util.Iterator;
import java.util.LinkedList;

//import android.util.Log;

/**
 * Numerical expression(formula) parser class
 * 
 * Parse the decimal numerical formula, and convert to LinkedList.
 * 
 * @author masanori
 * 
 */
public class ExpParser {
  protected LinkedList<String> list;
  protected String buf;
  
  /**
   * Parse a decimal numerical formula, and convert to a LinkedList.
   * @param exp Numerical formula (Decimal numbers)
   * @return Parsed LinkedList
   */
  public LinkedList<String> parseToList(String exp) {
    //Log.d("binCalc", "ExpParser.parseToList("+exp+")");
    // TODO I will rewrite it completely :p
    
    /* initialize list and buffer */
    list = new LinkedList<String>();
    buf = new String();
    int flagInBracket = 0;
    
    /* processing every one character from mathematical-expression  */
    for (int i = 0; i < exp.length(); i++) {
      char c = exp.charAt(i);
      
      /* Ignore characters */
      if(c == ',' || c == ' '){
        // if space ...
        continue;
      }
      
      /* Bracket process */
      if (c == ')') {
        // if close-bracket...
        
        _bufPush();
        
        while (flagInBracket > 0) {
          // if bracket has been already opening... its all closed now.
          
          list.addLast(")");
          flagInBracket--;
        }
        
      } else if (c == '*' || c == '/'){
        // if multiplication or division operator... it into bracket
        
        if(_returnListLastChar() == ')'){
          _bufPush();
          _chunkBeforeInsert("(");
          flagInBracket++;
        }else{
          list.addLast("(");
          _bufPush();
          flagInBracket++;
        }
        
      }else if (c == '+' || c == '-') {
        // if plus or minus operator...
        
        if (buf.contentEquals("+") || buf.contentEquals("-")  || buf.contentEquals("*") || buf.contentEquals("/")) {
          _bufPush();
          // if operators continued...  it into bracket (for negative-number)
          buf += "(";
          _bufPush();
          flagInBracket++;
        }else if (buf.length() == 0 && list.size() == 0){
          // start bracket (for FIRST number (negative-number))
          buf += "(";
          _bufPush();
          flagInBracket++;
        }
        _bufPush();
        
      } else {
        // if not operator...
        
        if (buf.contentEquals("(")) {
          // if open-bracket has been already in the buffer...
          _bufPush();
        }
        
        if (_returnListLastChar() != '('
            && (buf.contentEquals("+") || buf.contentEquals("-")
              || buf.contentEquals("*") || buf.contentEquals("/"))
          ) {
          _bufPush();
        }
      }
      
      /* Add char to buf */
      buf += c;
      
      if(c == ')'){
        // if close-bracket... push to List, immediately.  
        _bufPush();
      }
      
    }

    /* Push a remaining buffer to list */
    if (buf.length() > 0) {
      while (flagInBracket > 0) {
        _bufPush();
        buf += ")";
        flagInBracket--;
      }
      _bufPush();
    }
    
    //Log.d("binCalc", "parseToList done.");
    return list;
  }
  
  protected char _returnListLastChar() {
    if (list.isEmpty() == true) {
      return '\n';
    }
    String last = list.getLast().toString();
    return last.charAt(last.length() - 1);

  }

  protected void _bufPush() {
    if(buf.length() != 0){
      list.addLast(buf);
      buf = "";
    }
  }
  
  protected void _chunkBeforeInsert(String insertStr){
    int bracket_num = 0, insert_position = 0;
    
    /* find before the last chunk */
    for(int i=list.size()-1; i>=0; i--){
      if(list.get(i).contentEquals(")")){
        bracket_num++;
      }else if(list.get(i).contentEquals("(")){
        bracket_num--;
        if(bracket_num == 0){
          // if found before position...
          insert_position = i;
          break;
        }
      }
    }
    
    /* Making the new List, and insert the insertStr in found position. */
    LinkedList<String> newList = new LinkedList<String>();
    Iterator<String> iter = list.iterator();
    int i = 0;
    
    while(iter.hasNext()){
      String str = iter.next();
      if(i == insert_position){
        newList.addLast(insertStr);
      }
      newList.addLast(str);
      i++;
    }
    
    /* replace old List with new List */
    list = newList;
  }
}

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