This means that the real and imaginary parts of a Complex must now be
the same type. This seems like a real benefit: a Complex with a number real
part and a bigint imaginary part does not seem sensible.
Note that this is now straining typed-function in (at least) the following
ways:
(1) In this change, it was necessary to remove the logic that the square root
of a negative number calls complex square root, which then calls back
to the number square root in its algorithm. (This was creating a circular
reference in the typed-function which the old implementation of Complex
was somehow sidestepping.)
(2) typed-function could not follow conversions that would be allowed by
uninstantiated templates (e.g. number => Complex<number> if the latter
template has not been instantiated) and so the facility for
instantiating a template was surfaced (and for example is called explicitly
in the demo loader `extendToComplex`. Similarly, this necessitated
making the unary signature of the `complex` conversion function explicit,
rather than just via implicit conversion to Complex.
(3) I find the order of implementations is mattering more in typed-function
definitions, implying that typed-function's sorting algorithm is having
trouble distinguishing alternatives.
But otherwise, the conversion went quite smoothly and I think is a good demo
of the power of this approach. And I expect that it will work even more
smoothly if some of the underlying facilities (subtypes, template types) are
integrated into typed-function.
Glen Whitney
1444b9828f