Re: [Caml-list] The Implicit Accumulator: a design pattern using optional arguments

[Brian Hurt <bhurt@janestcapital.com>]

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Jon Harrop wrote:

>On Wednesday 27 June 2007 16:48:44 Mattias Engdegård wrote:
>  
>
>>The cost is a slightly clumsier use of symbols as strings (Symbol.str),
>>but my feeling is that the extra safety is worth it.
>>    
>>
>
>That is exactly what I did. Also, you cannot pattern match over the Sym.t but 
>I believe the OCaml compiler doesn't optimize pattern matches over strings 
>anyway.
>
>Incidentally, can we add this to the list of wanted optimizations: O(log n) 
>matching of strings, arrays and polymorphic variants.
>
>  
>
Actually, what I'd like is a more powerful regular expression engine- 
one where I can give multiple different patterns with constant values, 
and create a single regular expression that if the first pattern is 
matched, the first constant value is matched, etc.  Something with a 
signature like:

type 'a regex_t
val compile : (string * 'a) -> default:'a -> 'a regex_t
val re_match : 'a regex_t -> string -> 'a

Which would allow me to do stuff like:

let re = compile [ ("foo", 1); ("bar", 2); ("baz", 3) ] ~default:(-1);;

let f str =
    match re_match re str with
    | 1 -> (* it's a foo *)
    | 2 -> (* it's a bar *)
    | 3 -> (* it's a baz *)
    | -1 -> (* it didn't match *)
;;

In other words, something like ocamllex, except dynamic.

Brian


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