Re: Design Patterns and Functional programming

S Perryman wrote:
No problem, on the understanding that "lots of useful opportunities" is
not equivalent to 'all usage scenarios' (although a type system could give
warnings etc for such scenarios as opposed to reporting nothing) .

Yes. Same for a pattern matcher:

# function 0 -> 1 | n -> 3 | 3 -> 4;;
Warning U: this match case is unused.
- : int -> int = <fun>

# function 0 -> 1;;
Warning P: this pattern-matching is not exhaustive.
Here is an example of a value that is not matched:
1
- : int -> int = <fun>

The art is in working out how powerful you can make your patterns and type
system without sacrificing such tests. ML chooses linear patterns over
closed sum types, which works very well in practice.

--
Dr Jon D Harrop, Flying Frog Consultancy
The OCaml Journal
http://www.ffconsultancy.com/products/ocaml_journal/?usenet
.

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