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