On Wednesday, 15 June 2016 at 18:34:15 UTC, tsbockman wrote:
On Wednesday, 15 June 2016 at 16:40:19 UTC, Andrei Alexandrescu
wrote:
Getting to the design: the root of the problem is a byzantine
design that is closed to extension.
The design was closed deliberately because of (8). Template
bloat is a major concern, even with the current finite design.
I want `checkedint` to be usable in public APIs, and that
requires some standardization of error handling and base types
to be enforced upon the users. Otherwise, everyone will choose
something different and all template instantiations involving
integer types will become practically single-use.
Looking at the IntFlagPolicy, it offers three canned behavior:
throws, asserts, and noex.
The choice of policies is motivated by the natural
incompatibility of (2), (4), (6), and (7). I built in enough
variety to allow people to choose their own priorities among
those goals, and no more because of (8).
Re-reading what I wrote there, I makes it sound like the closed
design was motivated solely by template bloat concerns. But,
that's not true either.
Standardizing the error handling methods is also important for
other interoperability-related reasons:
* If every third-party library designs a different error
handling method,
people writing applications that depend on many libraries
will have to
study the `checkedint` error signaling of each one, and
make sure that
their code which interacts with each library knows how to
detect and
respond to its particular signaling mechanism.
My design for `checkedint` reduces the number of
`checkedint`-specific
signaling methods that need to be studied down to one (the
sticky flags
policy). The other two policies are just using D's standard
error-
handling facilities, and don't require any user
intervention anyway,
unless you want to catch the exception for some reason.
Even the sticky flags policy is only of concern for
`nothrow @nogc` APIs,
which I suspect in practice will mostly mean game libraries.
* The relative simplicity of my policy set has allowed me to
arrange them
into a strict linear hierarchy, so that the results of
mixing policies
is predictable and safe.
