method

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v1_9_2_180 - Show latest stable - 0 notes - Class: Bignum

[](p1) public

Bit Reference—Returns the nth bit in the (assumed) binary representation of big, where big[0] is the least significant bit.

a = 9**15
50.downto(0) do |n|
  print a[n]
end

produces:

000101110110100000111000011110010100111100010111001

Show source

static VALUE
rb_big_aref(VALUE x, VALUE y)
{
    BDIGIT *xds;
    BDIGIT_DBL num;
    VALUE shift;
    long i, s1, s2;

    if (TYPE(y) == T_BIGNUM) {
        if (!RBIGNUM_SIGN(y))
            return INT2FIX(0);
        bigtrunc(y);
        if (RBIGNUM_LEN(y) > DIGSPERLONG) {
          out_of_range:
            return RBIGNUM_SIGN(x) ? INT2FIX(0) : INT2FIX(1);
        }
        shift = big2ulong(y, "long", FALSE);
    }
    else {
        i = NUM2LONG(y);
        if (i < 0) return INT2FIX(0);
        shift = (VALUE)i;
    }
    s1 = shift/BITSPERDIG;
    s2 = shift%BITSPERDIG;

    if (s1 >= RBIGNUM_LEN(x)) goto out_of_range;
    if (!RBIGNUM_SIGN(x)) {
        xds = BDIGITS(x);
        i = 0; num = 1;
        while (num += ~xds[i], ++i <= s1) {
            num = BIGDN(num);
        }
    }
    else {
        num = BDIGITS(x)[s1];
    }
    if (num & ((BDIGIT_DBL)1<<s2))
        return INT2FIX(1);
    return INT2FIX(0);
}

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