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Subject: Re: [Caml-list] Purity in ocaml

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> On the other hand if types are annotated with the exceptions they
> throw then they become just another return value and become pure.
> Same input, same exception every time.
>

As far as Yotam Barnoy's goal is concerned, this isn't true. He wants to be
able to use purity annotations for optimisation: a most typical
optimisation which is valid only for pure functions is to rewrite *map f
(map g l)* into *map (f=E2=88=98g) l*. This optimisation, as it happens, is=
 not
valid with exception throwing functions as it may very well throw a
different exception.

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><div class=3D"gmail_quote">=
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left:1px solid rgb(204,204,204);padding-left:1ex">
On the other hand if types are annotated with the exceptions they<br>
throw then they become just another return value and become pure.<br>
Same input, same exception every time.<br></blockquote><br></div>As far=20
as Yotam Barnoy&#39;s goal is concerned, this isn&#39;t true. He wants to b=
e=20
able to use purity annotations for optimisation: a most typical=20
optimisation which is valid only for pure functions is to rewrite <i>map f =
(map g l)</i> into <i>map (f=E2=88=98g) l</i>. This optimisation, as it hap=
pens, is not valid with exception throwing functions as it may very well th=
row a different exception.<br>

</div></div>

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