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Annotation of 43BSD/contrib/icon/operators/power.c, revision 1.1.1.1

1.1       root        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:    }
                     76: 

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