Re: [Camllist] Haskell features in O'Caml

Arturo Borquez
 Mattias Waldau
 Florian Hars
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Date:  20010923 (19:40) 
From:  Florian Hars <florian@h...> 
Subject:  Re: [Camllist] Haskell features in O'Caml 
Arturo Borquez schrieb am Sat, Sep 22, 2001 at 07:56:36AM 0700: > On Sat, 22 September 2001, Steven Murdoch wrote: > > The main one I would like is the type assertion facility of Haskell. > > For example, one might write: > > mul :: Int > Int > Int > > mul a b = a * b > > As Ocaml is strong typed function mul is resolved > to be an integer function (denoted by operator * only > valid to integers). Haskel is strongly typed, too, and does the same type checking. The question was about type annotations, not type inference. The correct answer might have been a reference to the module system. You can specify the type of a function either in a separate *.mlifile or in an explicit module declaration: # module M : sig val mul : int > int > int end = struct let mul a b = a * b end;; module M : sig val mul : int > int > int end # M.mul 2 3;;  : int = 6 # module N : sig val mul : int > int > int end = struct let mul a b = a *. b (* Arithmetic is monomorphic  no type classes *) end;; Signature mismatch: Modules do not match: [...] The other question was about infix notation: > > For example if max gives the maximum of two arguments > > it can be applied normally, i.e. "max 2 3" will return 3, but "2 > > `max` 3" will also return 3. This is missing in Ocaml (some regard this as an asset, don't ask me why). > > Also if a function is named using operator symbols it can be used as > > an operator, e.g if &&& is defined as: > Ocaml: > # let ( &&& ) x y = if x >= y then x else y;; But you cannot change the fixity, it is defined by the first char of the operator, ie. ++, +*/ and +@%&! all have the same precedence and associativity as +. Of course, these are syntax issues, and you can change the syntax using camlp4: # EXTEND expr: AFTER "apply" [[ f=expr; "{"; "["; g=expr; "]"; "}"; h=expr > <:expr< $g$ $f$ $h$ >> ]]; END;;  : unit = () # let mul a b = a * b;; val mul : int > int > int = <fun> # 3 {[mul]} 4;;  : int = 12 # 3 {[fun a b > a * a + 2 * a * b + b * b]} 4;;  : int = 49 > > This can lead to some very easy to read programs Yes. And messing around with delimeters may introduce subtle bugs elsewhere... [[f=expr; "<"; g=LIDENT; ">"; h=expr > <:expr< $lid:g$ $f$ $h$ >> ]]; might be better if you do not want to write applications of anonymous functions in infix notation. Yours, Florian.  #!/bin/sh  set  `type p $0` 'tr [am][nz][AM][NZ]@/ [nz][am][NZ][AM]/@' fu '$UBZ\ R@.fvtangher' echo;while [ "$5" != "" ];do shift;done;$4 "gbhpu $3;znvy s/unef\ .qr<$3&&frq a rc "`$4 " $0"$1`">$3;rpub 'Jr ner Fvt bs Obet.'"$1`$4 $2$1`  Bug reports: http://caml.inria.fr/bin/camlbugs FAQ: http://caml.inria.fr/FAQ/ To unsubscribe, mail camllistrequest@inria.fr Archives: http://caml.inria.fr