Function: bcmod version 477

Function:
Description: Get the modulus of the left_operand using modulus.
Version:
Status: obsolete
Date: 2012-03-16 21:05
Summary: Fixing typo, 'last_operand' should have been 'left_operand'.
Programmer: jj5
Code
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/*
Note: this function is a hack, and it only supports the use cases I require at
the moment, being: arbitrary precision integer left_operand and native precision positive integer modulus (must fit in a native number, i.e. a double).
*/
function bcmod( left_operand, modulus ) {
  var i, d;
  function split( operand ) {
    var parts = operand.split( '.' );
    i = parts[ 0 ];
    d = '0.' + ( parts.length > 1 ? parts[ 1 ] : '0' );
  }  
  //modulus = Math.round( parseFloat( modulus ) );
  modulus = parseFloat( modulus );
  modulus = abs( modulus );
  if ( modulus < 1 ) { return null; }
  var take = 4;
  var modulus_limit = Math.pow( 10, take );
  if ( modulus >= modulus_limit  ) {
    throw new Error( "Modulus cannot be " + modulus_limit + " or greater." );
  }
  var result = 0;
  split( left_operand );
  var read_length = 0;
  function read() {
    read_length = i.length < take ? i.length : take;
    var result = i.substr( 0, take );
    i = i.substr( take );
    return result;
  }
  do {
    var n = parseInt( read() );
    result = ( result * read_length + n ) % modulus;
  }
  while ( i.length > 0 );
  result += parseFloat( d );
  var test = result - modulus;
  result = test < 0 ? result : test;
  return result.toString();
}
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