3 ms·

> I'll give it 2 weeks until someone releases a framework allowing you to write functions that don't compile unless their input is a prime number. Honestly tha

• pmiller2 9y ago
  I believe "don't compile," in this context, is short for "their compilation doesn't halt." That seems like a bad thing to me. ;)
  • myusernameisok 9y ago
    I don't understand how this is fundamentally different from just doing it in regular javascript. You could write a javascript function that recurses forever on condition x: just write a function that calls itself with the same parameters unless condition x is met. How is it fundamentally different if the type system does it?
    • shusson 9y ago
      > How is it fundamentally different if the type system does it? runtime vs compile time. For example someone could write some TypeScript that would forever compile, which is intuitively unexpected when compiling.
      • deleted 9y ago
        [deleted]
  • mmalone 9y ago
    Not necessarily. You should be able to write a halting computation to determine whether a number is prime in a Turing complete language. It may be stupid hard to encode, or take a really long time to run, however. The halting problem says that you can't write a halting decision procedure that takes an arbitrary program as input and determines whether that program halts, for any program. That doesn't mean that no programs halt. On the contrary, most programs in Turing complete languages obviously do halt and it's often trivial to tell if a particular program halts or not (e.g., `print "hello"` obviously halts). A Turing complete language can compute anything that is computable. So if the type system is Turing complete, you should be able to type a function that only takes primes... in theory.