4.3BSD - /usr/src/new/icon/operators/power.c

   1: #include "../h/rt.h"
   2: 
   3: /*
   4:  * x ^ y - raise x to the y power.
   5:  */
   6: 
   7: power(nargs, arg2, arg1, arg0)
   8: int nargs;
   9: struct descrip arg2, arg1, arg0;
  10:    {
  11:    register int t1, t2;
  12:    union numeric n1, n2;
  13:    extern double pow();
  14:    extern long ipow();
  15: 
  16:    SetBound;
  17:    /*
  18:     * x and y must be numeric.  Save the cvnum return values for later use.
  19:     */
  20:    if ((t1 = cvnum(&arg1, &n1)) == NULL)
  21:       runerr(102, &arg1);
  22:    if ((t2 = cvnum(&arg2, &n2)) == NULL)
  23:       runerr(102, &arg2);
  24: 
  25:    if (t1 == T_LONGINT && t2 == T_LONGINT)
  26:       /*
  27:        * Both x and y are integers.  Perform integer exponentiation
  28:        *  and place the result in arg0 as the return value.
  29:        */
  30:       mkint(ipow(n1.integer, n2.integer), &arg0);
  31:    else {
  32:       /*
  33:        * Either x or y is real, convert the other to a real, perform
  34:        *  real exponentiation and place the result in arg0 as the
  35:        *  return value.
  36:        */
  37:       if (t1 == T_LONGINT)
  38:          n1.real = n1.integer;
  39:       if (t2 == T_LONGINT)
  40:          n2.real = n2.integer;
  41:       if (n1.real == 0.0 && n2.real <= 0.0)
  42:          /*
  43:           * Tried to raise zero to a negative power.
  44:           */
  45:          runerr(204, NULL);
  46:       if (n1.real < 0.0 && t2 == T_REAL)
  47:          /*
  48:           * Tried to raise a negative number to a real power.
  49:           */
  50:          runerr(206, NULL);
  51:       mkreal(pow(n1.real,n2.real), &arg0);
  52:       }
  53:    ClearBound;
  54:    }
  55: 
  56: Opblock(power,2,"^")
  57: 
  58: long ipow(n1, n2)
  59: long n1, n2;
  60:    {
  61:    long result;
  62: 
  63:    if (n1 == 0 && n2 <= 0)
  64:       runerr(204, NULL);
  65:    if (n2 < 0)
  66:       return (0.0);
  67:    result = 1L;
  68:    while (n2 > 0) {
  69:       if (n2 & 01L)
  70:          result *= n1;
  71:       n1 *= n1;
  72:       n2 >>= 1;
  73:       }
  74:    return (result);
  75:    }

Defined functions