anchor.diff:  
       r(1) = r4_uniform_01 ( seed )
   
  -    if ( r(1) == 0.0E+00 ) then
  +    if ( abs(r(1))  <= 1.0E-10 ) then
         write ( *, '(a)' ) ' '
         write ( *, '(a)' ) 'R4VEC_NORMAL_AB - Fatal error!'
         write ( *, '(a)' ) '  R4_UNIFORM_01 returned a value of 0.'
  
positive.code: 
      r(1) = r8_uniform_01 ( seed )
  
      if ( r(1) == 0.0D+00 ) then
        write ( *, '(a)' ) ' '
        write ( *, '(a)' ) 'R8VEC_NORMAL_AB - Fatal error!'
        write ( *, '(a)' ) '  R8_UNIFORM_01 returned a value of 0.'
  
negative.code: 
    k = seed / 127773
  
    seed = 16807 * ( seed - int(k) * 127773 ) - int(k) * 2836
  
    if ( seed < 0 ) then
      seed = seed + 2147483647
  