#! /usr/bin/env python
#
def rat_to_dec ( top, bot ):

#*****************************************************************************80
#
## RAT_TO_DEC converts a rational to a decimal representation.
#
#  Discussion:
#
#    A rational value is represented by TOP / BOT.
#
#    A decimal value is represented as MANTISSA * 10^EXPONENT.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license. 
#
#  Modified:
#
#    11 June 2015
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, integer TOP, BOT, the rational value.
#
#    Output, integer MANTISSA, EXPONENT, the decimal number.
#
  from i4_gcd import i4_gcd

  if ( top == 0 ):
    mantissa = 0
    exponent = 0
    return mantissa, exponent

  gcd = i4_gcd ( top, bot )
  top = ( top // gcd )
  bot = ( bot // gcd )

  if ( bot < 0 ):
    top = -top
    bot = -bot

  if ( bot == 1 ):
    mantissa = top
    exponent = 0
    return mantissa, exponent

  exponent = 0

  while ( ( bot % 10 ) == 0 ):
    exponent = exponent - 1
    bot = ( bot // 10 )

  while ( ( top % 10 ) == 0 ):
    exponent = exponent + 1
    top = ( top // 10 )

  r = float ( top ) / float ( bot )

  if ( r < 0.0 ):
    s = -1
    r = -r
  else:
    s = 1

  while ( r != round ( r ) ):
    r = r * 10.0
    exponent = exponent - 1

  mantissa = s * r

  return mantissa, exponent

def rat_to_dec_test ( ):

#*****************************************************************************80
#
## RAT_TO_DEC_TEST tests RAT_TO_DEC.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    11 June 2015
#
#  Author:
#
#    John Burkardt
#
  import platform
  from dec_to_rat import dec_to_rat
  from i4_uniform_ab import i4_uniform_ab

  print ( '' )
  print ( 'RAT_TO_DEC_TEST' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  RAT_TO_DEC fraction => decimal,' )
  print ( '' )
  print ( '  In this test, choose the top and bottom' )
  print ( '  of a rational at random, and compute the' )
  print ( '  equivalent real number.' )
  print ( '' )
  print ( '  Then convert to decimal, and the equivalent real.' )
  print ( '' )
  print ( '  Then convert back to rational and the equivalent real.' )
  
  seed = 123456789

  for i in range ( 0, 10 ):

    rat_top, seed = i4_uniform_ab ( -1000, 1000, seed )
    rat_bot, seed = i4_uniform_ab (     1, 1000, seed )

    r1 = float ( rat_top ) / float ( rat_bot )
    mantissa, exponent = rat_to_dec ( rat_top, rat_bot )
    r2 = float ( mantissa ) * 10.0 ** exponent
    rat_top2, rat_bot2 = dec_to_rat ( mantissa, exponent )
    r3 = float ( rat_top2 ) / float ( rat_bot2 )

    print ( '' )
    print ( '  %g = %d / %d' % ( r1, rat_top, rat_bot ) )
    print ( '  %g = %d * 10^%d' % ( r2, mantissa, exponent ) )
    print ( '  %g = %d / %d' % ( r1, rat_top2, rat_bot2 ) )
#
#  Terminate.
#
  print ( '' )
  print ( 'RAT_TO_DEC_TEST' )
  print ( '  Normal end of execution.' )
  return

if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( )
  rat_to_dec_test ( )
  timestamp ( )