Walter Bright Wrote: > Jason House wrote: > > Walter Bright Wrote: > > > >> Jason House wrote: > >>> 7. Compiler-assisted verification. > >> For interfaces, the compile time checking is limited to verifying that > >> functions with the right signature are supplied. Templates can go > >> considerably beyond that with the constraint checking. > > > > constraints are more powerful, but they have downsides: If a class is > > incorrectly defined, failure to use a type without a constraint check leads > > to errors in the code using it instead of the class definition. Usage isn't > > always guaranteed to be correct either, so the developer must spend extra > > time diagnosing the real error. If a class is incorrectly, initial usage > > without a constraint may completely miss the error. Easy examples would be a > > typo propogated with copy/paste, or neglecting to use save. If a class is > > incorrectly defined and usage uses a constraint, the developer will simply > > get an error that there is no matching call. If a constraint is > > incorrectly > > defined and usage uses the constraint, the developer will simply get an > > error > > that there is no matching call. > > > > None of these scenarios are particularly helpful for a developer > > creating/expanding a family of objects. > > > You can also make constraints that give custom error messages, so you can do > better than the compiler's stab at it. How good they are is up to the > designer > of the type.
So you're favoring an isXXX as well as a requireXXX? Such duplication is both annoying and error prone. Making isXXX use requieXXX under the hood ishigher implementation complexity. I don't know about others, but I was drawn to its simplicity over C++. Many have praised its ability to make template programming simple. This feels like a step backwards.
