We don't currently have a way to plug into pattern expressions, do we? I
was toying with the idea of having a simpler interface to the tre
package, and I was thinking it'd be nice if we could do something like:
match "hello" with
| "hi" => expr1
| regex2 => expr2
| regex3 => expr3
| regex4 as m:regex_match => expr4
| regex5 as s:list[string] => expr5
| regex6 => expr6
| "ho" => expr7
| _ => expr8
endmatch
where the ?m is some way to extract out the regular expression match
data. How possible would it be to do this? One way I thought it could be
done is to desugar into this:
// some more magic functions
fun __match_exists__ (x:regex, y:string):bool = ...;
fun __match__ (x:regex, y:string):opt[regex_match] = ...;
fun __match__ (x:regex, y:string):opt[list[string]] = ...;
val x = "hello"
match x with
| "hi" => expr1
| _ =>
if __match_exists__(regex2, x) then expr2
elif __match_exists__(regex3, x) then expr3
else
match (__match__ of regex_match)(regex4, x) with
| Some ?x => expr4
| None =>
match (__match__ of list[string])(regex5, x) with
| Some ?x => expr5
| None =>
if __match_exists__(regex6, x) then expr6
else
match x with
| "ho" => expr7
| _ => expr8
endmatch
endmatch
endmatch
How doable would this be?
-e
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