Task: Long multiplication



C#: using System;
using static System.Console;
using BI = System.Numerics.BigInteger;

class Program {

  static decimal mx = 1E28M, hm = 1E14M, a;

  
  struct bi { public decimal hi, lo; }

  
  static bi set4sq(decimal a) { bi r; r.hi = Math.Floor(a / hm); r.lo = a % hm; return r; }

  
  static string toStr(bi a, bool comma = false) {
    string r = a.hi == 0 ? string.Format("{0:0}", a.lo) :
                           string.Format("{0:0}{1:" + new string('0', 28) + "}", a.hi, a.lo);
    if (!comma) return r;  string rc = "";
    for (int i = r.Length - 3; i > 0; i -= 3) rc = "," + r.Substring(i, 3) + rc;
    return r.Substring(0, ((r.Length + 2) % 3) + 1) + rc; }

  
  static decimal Pow_dec(decimal bas, uint exp) {
    if (exp == 0) return 1M; decimal tmp = Pow_dec(bas, exp >> 1); tmp *= tmp;
    if ((exp & 1) == 0) return tmp; return tmp * bas; }

  static void Main(string[] args) {
    for (uint p = 64; p < 95; p += 30) {        
      bi x = set4sq(a = Pow_dec(2M, p)), y;     
      WriteLine("The square of (2^{0}):                    {1,38:n0}", p, a); BI BS = BI.Pow((BI)a, 2);
      y.lo = x.lo * x.lo; y.hi = x.hi * x.hi;   
      a = x.hi * x.lo * 2M;                     
      y.hi += Math.Floor(a / hm);               
      y.lo += (a % hm) * hm;                    
      while (y.lo > mx) { y.lo -= mx; y.hi++; } 
      WriteLine(" is {0,75} (which {1} match the BigInteger computation)\n", toStr(y, true),
          BS.ToString() == toStr(y) ? "does" : "fails to"); } }

}







COBOL:        identification division.
       program-id. long-mul.
       data division.
       replace ==ij-lim== by ==7== ==ir-lim== by ==14==.
       working-storage section.
       1 input-string pic x(26) value "18,446,744,073,709,551,616".
       1 a-table.
        2 a pic 999 occurs ij-lim.
       1 b-table.
        2 b pic 999 occurs ij-lim.
       1 ir-table value all "0".
        2 occurs ij-lim.
         3 ir pic 999 occurs ir-lim.
       1 s-table value all "0".
        2 s pic 999 occurs ir-lim.
       1 display.
        2 temp-result pic 9(6) value 0.
        2 carry pic 999 value 0.
        2 remain pic 999 value 0.
       1 binary.
        2 i pic 9(4) value 0.
        2 j pic 9(4) value 0.
        2 k pic 9(4) value 0.
       procedure division.
       begin.
           move 1 to j
           perform varying i from 1 by 1 until i > ij-lim
               unstring input-string delimited ","
                   into a (i) with pointer j
           end-perform
           move a-table to b-table
           perform intermediate-calc
           perform sum-ir
           perform display-result
       stop run
       .

       intermediate-calc.
           perform varying i from ij-lim by -1 until i < 1
               move 0 to carry
               perform varying j from ij-lim by -1 until j < 1
                   compute temp-result = a (i) * b (j) + carry
                   divide temp-result by 1000 giving carry
                       remainder remain
                   compute k = i + j
                   move remain to ir (i k)
               end-perform
               subtract 1 from k
               move carry to ir (i k)
           end-perform
           .

       sum-ir.
           move 0 to carry
           perform varying k from ir-lim by -1 until k < 1
               move carry to temp-result
               perform varying i from ij-lim by -1 until i < 1
                   compute temp-result = temp-result + ir (i k)
               end-perform
               divide temp-result by 1000 giving carry
                   remainder remain
               move remain to s (k)
           end-perform
           .

       display-result.
           display "   " input-string
           display " * " input-string
           display " = " with no advancing
           perform varying k from 1 by 1
           until k > ir-lim or s (k) not = 0
           end-perform
           if s (k) < 100
               move 1 to i
               inspect s (k) tallying i for leading "0"
               display s (k) (i:) "," with no advancing
               add 1 to k
           end-if
           perform varying k from k by 1 until k > ir-lim
               display s (k) with no advancing
               if k < ir-lim
                   display "," with no advancing
               end-if
           end-perform
           display space
           .

       end program long-mul.