/*  slflpow.cpp  by K.Tsuru  */
// function ID 2002   DRADIX, BRADIX
/**************************************************************
SLong and SInteger classes
It provides to the n-th powewr of x(x^n) Knuth's binary method.
***************************************************************/
#ifndef SN_H
#include "sn.h"
#endif
#include <iostream>

SLong Lpow(const SLong& x, ulong n){
    if(!x.Sign(2002)) return x;     // x = 0
    int sgn = 1;
    uint h = x.Head();
    if(x.Sign() < 0) sgn = (n & 1) ? -1 : 1;

    if(!n) return SLong(x.Type(), minArraySize, 1L);        // return 1;
    if(x.IsOne()) return SLong(x.Type(), minArraySize, sgn);    // |x| = 1;

    fType rdx = x.Radix();
//It estimates the number of figures which needs to store the result.
//x has an order of x[h]*(R^h).
    ulong fig;
    fig = ulong( (double)n*(log10((double)x[h])/log10((double)rdx) + (double)h) )+1u;
    //figures in radix

    if(fig > x.MaxSize()) {
        cerr << "fig = " << fig << " n= " << n << endl;
        x.SetError(x.OVERFLOW_ERR,"Lpow", 2002);
    }
/*
The necessary figues is known, then it allocates its memory.
If the out of memory error occures the program terminates here.
*/
    SLong y( x.Type(), (uint)fig), z( x.Type(), (uint)fig); // cutDown = DISABLE
    y = 1;  z = x;  //To make the size same as that of y it does not use z(x).
    if(x.Sign() < 0) z.ChangeSign();    // z > 0

    while(1){
        if( n & 1 ) y *= z;
        n /= 2;
        if( !n ) break;
        z *= z;
    }
    if(sgn < 0) y.ChangeSign();
    return y;
}