Re: [Caml-list] Should -strict-sequence become the default?

[John Whitington <john@coherentgraphics.co.uk>]

Hi,

Yaron Minsky wrote:
> Back in 3.12.1, a flag, -strict-sequence, was added that require that
> the left-hand side of a sequence returns unit.  I suspect there's
> broad agreement that -strict-sequence is the better default, but that
> the old behavior has been left in place by default for compatibility
> reasons.  I wonder if in the next major release, it would make sense
> to make -strict-sequence the default, and have a flag for enabling the
> old behavior.
>
> To say the obvious, such a change would be of no value to experienced
> people and organizations that know how to set up the compiler to their
> liking, but can be of real value to newcomers to the language.

Isn't this covered (as a warning not an error) by warnings 5 & 10, both 
of which are default?

Although the manual does say, rather ominously...

"Note that warnings 5 and 10 are not always triggered, depending on the 
internals of the type checker."

Does that caveat also apply to -strict-sequence? If not, why not, and 
could its implementation be back-ported to fix up warnings 5 and/or 10?

feast:~ john$ ocaml -strict-sequence
         OCaml version 4.01.0

# let f x = x + 1;;
val f : int -> int = <fun>
# f 1; 0;;
Error: This expression has type int but an expression was expected of 
type unit

feast:~ john$ ocaml
         OCaml version 4.01.0

# let f x = x + 1;;
val f : int -> int = <fun>
# f 1; 0;;
Warning 10: this expression should have type unit.
- : int = 0

The warning text for warning 10 could be changed to:

"Warning 10: this expression should have type unit. If this is intended, 
consider using the 'ignore' function."

Cheers,

-- 
John Whitington
Director, Coherent Graphics Ltd
http://www.coherentpdf.com/