function(a, b, c, d)               //text and three dummy arguments
{
  d = '';                          //compile path for the current string
  for (b = 0; c = a.charAt(b++); ) //for each character in the string
    d += z[c] ||                   //append path from the character map or
         z._;                      //use the underscore for undefined characters
  b = /[hlm]([--9]+)/g;            //match first number from all horizontal/line/move commands
  for (; c = b.exec(d); )          //for each match in the compiled path
    y[2] += +c[1];                 //expand viewBox by the matched width, converted to a number
  x += d;                          //append the compiled path to the XML fragment
  return this                      //make the method call chainable
}