From: Jacques Garrigue <garrigue@kurims.kyoto-u.ac.jp>
To: henridf@lcavsun1.epfl.ch
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] 'should have type unit' warning in 'let _ =' ?
Date: Tue, 15 Jul 2003 10:04:36 +0900 [thread overview]
Message-ID: <20030715100436I.garrigue@kurims.kyoto-u.ac.jp> (raw)
In-Reply-To: <Pine.LNX.4.44.0307150220570.6294-100000@lcmpc4.epfl.ch>
From: henridf@lcavsun1.epfl.ch
> i had a minor bug where the last expression in a
> let _ = ...
> block of my module was not fully applied and hence was returning a
> functional value rather than apply the function (because I had added a
> parameter to the function).
>
> pretty harmless, but it led me to wonder why I wasn't writing 'let () =
> ..' for all my module initialization blocks, which would have given me
> 'warning should have type unit' in the above situation.
>
> So is there a reason why the commonly used idiom seems to be 'let _ ='
> rather than 'let () = '?
I suppose this is the 1 character difference :-)
Programmers are lazy.
I've been advocating using "let () =" for a while now, and I am of
course using it myself.
By the way, there is a reason "let _ =" produces no warning: this is
the only way to do a partial application without warning.
"expr; ..." and even "ignore (expr); ..." will produce a warning.
By the way, I'm always disabling the s warning ("should be unit"), to
avoid being tempted by using "let _ = expr in " when I want to ignore
the result of a fully applied expression which does not return unit.
I know ignore does it, but I'm lazy too.
Jacques
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next prev parent reply other threads:[~2003-07-15 1:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-15 0:29 henridf
2003-07-15 1:04 ` Jacques Garrigue [this message]
2003-07-15 11:36 ` Richard Jones
2003-07-16 0:10 ` Jacques Garrigue
2003-07-16 7:11 ` Jean-Christophe Filliatre
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