3 ms·

> In CL, type specifications are promises to the compiler, not specifications of program semantics. Then they aren't types.

• rurban 9y ago
  Most of them are type hints. Perl6 and cperl have a similar distinction. Hard types and compiler hints. In an FFI context it's a hard type, with arrays or structs also, with primitives the compiler may ignore it or allow otherwise permitted temporary casts.
  • catnaroek 9y ago
    > Most of them are type hints. Perl6 and cperl have a similar distinction. Why are so-called “type hints” interesting in? The real value in a type system is: (0) Not having to worry about large classes of mistakes. They just don't happen in a legal program. (1) Enforcing abstractions, i.e., not allowing library users to make decisions based on library implementation details. (2) Managing the verification effort. Proving that a program meets its specification becomes much easier when components are guaranteed not to violate the assumptions made in each other's design. A “type system” that can't do any of these is just a waste of engineering effort.
    • rurban 9y ago
      Yes, and much more. types also allows lowering generic ops to fast ops, which is typically 10x faster then without types.
      • catnaroek 9y ago
        I'd love to read about how you can use so-called “type hints” to mechanically rule out programs that inspect the internal representation of abstractions provided by third parties.