BigInt.opCast

assert(cast(float)  BigInt("35540592535949172786332045140593475584")
        == 35540592535949172786332045140593475584.0f);
assert(cast(double) BigInt("35540601499647381470685035515422441472")
        == 35540601499647381470685035515422441472.0);
assert(cast(real)   BigInt("35540601499647381470685035515422441472")
        == 35540601499647381470685035515422441472.0L);

assert(cast(float)  BigInt("-0x1345_6780_0000_0000_0000_0000_0000") == -0x1.3456_78p+108f       );
assert(cast(double) BigInt("-0x1345_678a_bcde_f000_0000_0000_0000") == -0x1.3456_78ab_cdefp+108 );
assert(cast(real)   BigInt("-0x1345_678a_bcde_f000_0000_0000_0000") == -0x1.3456_78ab_cdefp+108L);

// BigInts whose values cannot be exactly represented as float/double/real
// are rounded when cast to float/double/real. When cast to float or
// double or 64-bit real the rounding is strictly defined. When cast
// to extended-precision real the rounding rules vary by environment.

// BigInts that fall somewhere between two non-infinite floats/doubles
// are rounded to the closer value when cast to float/double.
assert(cast(float) BigInt(0x1aaa_aae7) == 0x1.aaa_aaep+28f);
assert(cast(float) BigInt(0x1aaa_aaff) == 0x1.aaa_ab0p+28f);
assert(cast(float) BigInt(-0x1aaa_aae7) == -0x1.aaaaaep+28f);
assert(cast(float) BigInt(-0x1aaa_aaff) == -0x1.aaaab0p+28f);

assert(cast(double) BigInt(0x1aaa_aaaa_aaaa_aa77) == 0x1.aaa_aaaa_aaaa_aa00p+60);
assert(cast(double) BigInt(0x1aaa_aaaa_aaaa_aaff) == 0x1.aaa_aaaa_aaaa_ab00p+60);
assert(cast(double) BigInt(-0x1aaa_aaaa_aaaa_aa77) == -0x1.aaa_aaaa_aaaa_aa00p+60);
assert(cast(double) BigInt(-0x1aaa_aaaa_aaaa_aaff) == -0x1.aaa_aaaa_aaaa_ab00p+60);

// BigInts that fall exactly between two non-infinite floats/doubles
// are rounded away from zero when cast to float/double. (Note that
// in most environments this is NOT the same rounding rule rule used
// when casting int/long to float/double.)
assert(cast(float) BigInt(0x1aaa_aaf0) == 0x1.aaa_ab0p+28f);
assert(cast(float) BigInt(-0x1aaa_aaf0) == -0x1.aaaab0p+28f);

assert(cast(double) BigInt(0x1aaa_aaaa_aaaa_aa80) == 0x1.aaa_aaaa_aaaa_ab00p+60);
assert(cast(double) BigInt(-0x1aaa_aaaa_aaaa_aa80) == -0x1.aaa_aaaa_aaaa_ab00p+60);

// BigInts that are bounded on one side by the largest positive or
// most negative finite float/double and on the other side by infinity
// or -infinity are rounded as if in place of infinity was the value
// `2^^(T.max_exp)` when cast to float/double.
assert(cast(float) BigInt("999_999_999_999_999_999_999_999_999_999_999_999_999") == float.infinity);
assert(cast(float) BigInt("-999_999_999_999_999_999_999_999_999_999_999_999_999") == -float.infinity);

assert(cast(double) BigInt("999_999_999_999_999_999_999_999_999_999_999_999_999") < double.infinity);
assert(cast(real) BigInt("999_999_999_999_999_999_999_999_999_999_999_999_999") < real.infinity);