Modify a text file: $/getdec1a.java

$/getdec1a.java

//// Convert keyboard input to a decimal number.
//// bam:2a20: getdec1a.java
String title="Convert keyboard input to a decimal number.";
String who="B.A.Martin: 2012/10/20 getdec1a.java";

String digits="";      // String of digits entered (but not decoded).
String results="";     // List of previous results.
int number=-1;         // Most-recent number decoded.

boolean debug=false;        // DEBUG
int nsave, msave;
String old="";

void setup() {
  //// Set up screen size.
  size( 400, 300 );
}
void draw() {
  //// paint the background (and instructions), then display the number.
  background( 200,240,255 );
  scene();
  show();
}
void scene() {
  //// Title, signature, and instructions to user.
  fill(0);    // Black text.
  text( title, width/2-100, 10 );
  text( who, 20, height-20);
  //
  text( "Enter a number, using the keyboard.", 10, 50 );
  fill( 150,150,150 );
  text( "Space-bar to compute result.)", 10, 62 );  
  text( "q to quit.  = for debugging info.", 10, 74 );  
}
void show() {
  //// Display the string of digits.
  if (digits.length() > 0 ) {
    fill( 0,0,255 );
    text( "Digits entered so far:", 10, 100 );
    text( digits, 140, 100 );
  }      
  //// Display all previous results (if any).
  if (results.length() > 0 ) {
    fill(255,0,0);
    text( "Results:", 20, 150 );
    text( results, 20, 170 );
  }
  if (debug) debug();
}
void debug() {
    // DEBUG
    fill( 0,150,255 );
    text( "Length():   "+digits.length(), width-200, 100 );
    //
    if (old.length() > 0) {
      fill( 255,0,255 );
      int m=2;
      text( "Old number:      "+nsave, width-200, 100+12*m++ );
      text( "Old string:      "+old, width-200, 100+12*m++ );
      text( "Old multiplier:  "+msave, width-200, 100+12*m++ );
      text( "Old length:      "+old.length(), width-200, 100+12*m++ );
    }
}

//// EVENT HANDLERS ////

void keyPressed() {
  //// If key is a digit, just append  it to the string of digits.
  if ( key >= '0' && key <= '9' ) {
    //// Input a digit.
    int digit=  key - '0';
    digits = digits + digit;    // Append digit to string.
  } else if (key == '=') {
  } else if (key == '?') {
    debug=  ! debug;
  } else if (key == 'q') {
    exit();
    
    //++++ Check for . decimal point.
    // +++ Check for + -
    // +++ Also check for 'h' maybe 'e'
  } else if (key == ' ') {
    //// SPACE:  Decode the # and empty the string.
    compute();
  }
}
void compute() {
  //// Compute value of digits string.  Store in number.  Clear string.
    number=  dec( digits );   // Decode the string.
    results +=  number;      // Append number to result
    results +=  '\n';        // Append newline
    old=  digits;            // (Save old string for debugging.)
    digits=  "";             // Empty the string.
}
int dec( String s ) {
  //// Convert string to decimal.
  ////   number=  sum of a[j] * 10 ^ j
  int number;
  
  // Multiplier for  highest digit is 10^( # of digits minus 1 )
  int multiplier=  1;
  for ( int j=0; j< digits.length(); j++ ) {
    multiplier = multiplier * 10;
  }
  multiplier = multiplier / 10;

// DEBUG:  save multiplier.
  msave=  multiplier;

// Now, for each digit, extract the value and multiply.
  // Add that product to the total.
  number=  0;
  for ( int j=0; j< digits.length(); j++ ) {
    int d=  digits.charAt(j) - '0';
    number += d * multiplier;
    multiplier /= 10;
  }
  nsave=  number;  
  return number;
}