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bh=UsOPW0+gH3UtrCyGJZ1fKKIpfbnbb93+c8KZD/WLKis=; b=AwiG9lyGswcKRFXQ179cTAqD6WaXPCsycW4xb0T9o1Ymc3jdOIGWCtZN0sdA61Zo06 m5CDNrO4xheu4DJva/LMfwaIvHyal6o9zXoNEA6pob826VG3yW+Oghfbuti1Oi6ovnSh xNv4bEi34yDEqNWIGjLZEAgOcpStwrW0SCRq6j9VDL/+QVWJfda3m7GUBNs+vlHIADCg YUOvY8ngtBt/0PtFsjGWilO18A0rBTeeFKNsY5W46ZvcwRTdY4Pt+WiUNoZhL6DcPy8a iV7WkjAWfH0sa4q8LKOnIGOpZrEeDJU4vSAjE5FqCcTay5Eq/QIINcka3fF/L7sh5nzk PRbg== X-Gm-Message-State: APf1xPDR6U9iN1ZkjrGYOlkBrKP/Y0F5Gjc6A7n/pGRL9bsRQBGFWrCf vnW9vQvPVmawxUIke/KbnoWKRBlO3JznLaCQzUQ= X-Google-Smtp-Source: AH8x227OmjYXM7+710fXIvGFTXN5OqTC+OnkgVxX/3H1o7H+ZWY2PBMU28nD1i4PQFRO1wl0OfMdDgOwgDh/EBukgEo= X-Received: by 10.98.232.24 with SMTP id c24mr595292pfi.227.1518649380480; Wed, 14 Feb 2018 15:03:00 -0800 (PST) MIME-Version: 1.0 Received: by 10.100.133.136 with HTTP; Wed, 14 Feb 2018 15:02:59 -0800 (PST) In-Reply-To: <20180214195046.Horde.mSIwdxq5Yo9xUKgfzIss4Ey@webmail.in-berlin.de> References: <21BC6EDE-DB27-460B-A4D5-BBD583C9E899@TimLeonard.us> <20180214195046.Horde.mSIwdxq5Yo9xUKgfzIss4Ey@webmail.in-berlin.de> From: Chet Murthy Date: Wed, 14 Feb 2018 15:02:59 -0800 Message-ID: To: Oliver Bandel Cc: caml-list Content-Type: multipart/alternative; boundary="f4f5e80653c0dcaa5d0565341c9d" Subject: Re: [Caml-list] a question about syntax --f4f5e80653c0dcaa5d0565341c9d Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 wrote: > > Zitat von Tim Leonard (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=E2=80=99t the semicolon syntactically terminate the match expres= sion? >> > > No. > You can use semicolon to put more then one expression together. > So the "field2 =3D 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 =3D { field1 : bool; field2 : int };; >> >> let f x =3D { field1 =3D match x with _ -> true ; field2 =3D 2 };; (*= this >> fails *) >> > > Here I get "Error: Unbound value field2", > which is, because the match-case reaches until the }. > > > > >> let f x =3D { field1 =3D ( match x with _ -> true ); field2 =3D 2 };; (*= this >> is ok *) >> > > Here it works, because the match-statement is sorrounded / enclosed by ( > and ). > > Ciao, > Oliver > > > > -- > Caml-list mailing list. Subscription management and archives: > https://sympa.inria.fr/sympa/arc/caml-list > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners > Bug reports: http://caml.inria.fr/bin/caml-bugs > --f4f5e80653c0dcaa5d0565341c9d Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I remember back in the day Pierre Weis explaining to me th= at this syntactic trade-off was made in order to allow that
"let&q= uot; and "match" didn't have ending key-words (e.g. "end= ").=C2=A0 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 ca= use a syntax error?
Shouldn=E2=80=99t the semicolon syntactically terminate the match expressio= n?

 No.
You can use semicolon to put more then one expression together.
So the "field2 =3D 2" is seen as part of the match.

If you have a pattern matching, this way you can put multiple commands/expr= essions 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 ma= tch-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 =3D { field1 : bool; field2 : int };;

let f x =3D { field1 =3D=C2=A0 =C2=A0match x with _ -> true=C2=A0 ; fiel= d2 =3D 2 };; (* this fails *)

 Here I get "Error: Unbound value field2",
which is, because the match-case reaches until the }.




let f x =3D { field1 =3D ( match x with _ -> true ); field2 =3D 2 };; (*= this is ok *)

 Here it works, because the match-statement is sorrounded / enclosed by ( an= d ).

Ciao,
=C2=A0 Oliver



--
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