Re: [Caml-list] a question about syntax

[Chet Murthy <murthy.chet@gmail.com>]

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I remember back in the day Pierre Weis explaining to me that this syntactic
trade-off was made in order to allow that
"let" and "match" didn't have ending key-words (e.g. "end").  Unlike in
SML/NJ.

--chet--


On Wed, Feb 14, 2018 at 10:50 AM, Oliver Bandel <oliver@first.in-berlin.de>
wrote:

>
> Zitat von Tim Leonard <Tim@timleonard.us> (Tue, 13 Feb 2018 22:31:14
> -0500)
>
> A simple question of syntax: why does the first definition of function f
>> cause a syntax error?
>> Shouldn’t the semicolon syntactically terminate the match expression?
>>
>
> No.
> You can use semicolon to put more then one expression together.
> So the "field2 = 2" is seen as part of the match.
>
> If you have a pattern matching, this way you can put multiple
> commands/expressions in a row,
> without the need to use begin/end or ( ) in any match-case.
> It's the other way around: you need to put begin/end or ( ) around a
> match-statement.
>
> This way you have to add one such enclosing around a match-statement,
> instead of one such enclosing in any match-case of such a statement.
>
>
>
>> type my_record = { field1 : bool; field2 : int };;
>>
>> let f x = { field1 =   match x with _ -> true  ; field2 = 2 };; (* this
>> fails *)
>>
>
> Here I get "Error: Unbound value field2",
> which is, because the match-case reaches until the }.
>
>
>
>
>> let f x = { field1 = ( match x with _ -> true ); field2 = 2 };; (* this
>> is ok *)
>>
>
> Here it works, because the match-statement is sorrounded / enclosed by (
> and ).
>
> Ciao,
>   Oliver
>
>
>
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