arcmak.cpp

来自「This document is intended to serve as an」· C++ 代码 · 共 20 行

/*
    From NR book: 

    The routine arcmak constructs the cumulative frequency distribution table used
    to partition the interval at each stage. In the principal routine arcode, when an
    interval of size jdif is to be partitioned in the proportions of some n to some ntot,
    say, then we must compute (n*jdif)/ntot. With integer arithmetic, the numerator
    is likely to overflow; and, unfortunately, an expression like jdif/(ntot/n) is not
    equivalent. In the implementation below, we resort to double precision floating
    arithmetic for this calculation. Not only is this inefficient, but different roundoff
    errors can (albeit very rarely) make different machines encode differently, though any
    one type of machine will decode exactly what it encoded, since identical roundoff
    errors occur in the two processes. For serious use, one needs to replace this floating
    calculation with an integer computation in a double register (not available to the
    C programmer).

    The internally set variable minint, which is the minimum allowed number
    of discrete steps between the upper and lower bounds, determines when new lowsignificance
    digits are added. minint must be large enough to provide resolution of
    all the input characters. That is, we must have pi