coerce

        # Rational.coerce

(from ruby core)
### Implementation from Numeric
---
    coerce(other) -> array

---

Returns a 2-element array containing two numeric elements, formed from
the two operands `self` and `other`, of a common compatible type.

Of the Core and Standard Library classes, Integer, Rational, and Complex
use this implementation.

Examples:

    i = 2                    # => 2
    i.coerce(3)              # => [3, 2]
    i.coerce(3.0)            # => [3.0, 2.0]
    i.coerce(Rational(1, 2)) # => [0.5, 2.0]
    i.coerce(Complex(3, 4))  # Raises RangeError.

    r = Rational(5, 2)       # => (5/2)
    r.coerce(2)              # => [(2/1), (5/2)]
    r.coerce(2.0)            # => [2.0, 2.5]
    r.coerce(Rational(2, 3)) # => [(2/3), (5/2)]
    r.coerce(Complex(3, 4))  # => [(3+4i), ((5/2)+0i)]

    c = Complex(2, 3)        # => (2+3i)
    c.coerce(2)              # => [(2+0i), (2+3i)]
    c.coerce(2.0)            # => [(2.0+0i), (2+3i)]
    c.coerce(Rational(1, 2)) # => [((1/2)+0i), (2+3i)]
    c.coerce(Complex(3, 4))  # => [(3+4i), (2+3i)]

Raises an exception if any type conversion fails.