method

log2

v2_1_10 - Show latest stable - 0 notes - Class: Math

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log2(p1) public

Returns the base 2 logarithm of x.

Domain: (0, INFINITY)

Codomain: (-INFINITY, INFINITY)

Math.log2(1)      #=> 0.0
Math.log2(2)      #=> 1.0
Math.log2(32768)  #=> 15.0
Math.log2(65536)  #=> 16.0

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static VALUE
math_log2(VALUE obj, VALUE x)
{
    double d0, d;
    size_t numbits;

    if (RB_BIGNUM_TYPE_P(x) && RBIGNUM_POSITIVE_P(x) &&
            DBL_MAX_EXP <= (numbits = rb_absint_numwords(x, 1, NULL))) {
        numbits -= DBL_MANT_DIG;
        x = rb_big_rshift(x, SIZET2NUM(numbits));
    }
    else {
        numbits = 0;
    }

    Need_Float(x);
    d0 = RFLOAT_VALUE(x);
    /* check for domain error */
    if (d0 < 0.0) domain_error("log2");
    /* check for pole error */
    if (d0 == 0.0) return DBL2NUM(-INFINITY);
    d = log2(d0);
    d += numbits;
    return DBL2NUM(d);
}

log2

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