<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">On 20/10/15 19:47, Mike Meyer wrote:<br>
</div>
<blockquote
cite="mid:CAD=7U2BQwYegQ5C+oMYnmxbe-CJmTqcdgcLYTPo7e_Wr9S=yBA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_quote">
<div dir="ltr">On Tue, Oct 20, 2015 at 1:35 PM Gregory Collins
<<a moz-do-not-send="true"
href="mailto:greg@gregorycollins.net">greg@gregorycollins.net</a>>
wrote:</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">The point Johan is trying to
make is this: if I'm thinking of using Haskell, then
I'm taking on a lot of project risk to get a
(hypothetical, difficult to quantify) X% productivity
benefit. If choosing it actually <b>costs</b> me a
(real, obvious, easy to quantify) Y% tax because I
have to invest K hours every other quarter fixing all
my programs to cope with random/spurious changes in
the ecosystem and base libraries, then unless we can
clearly convince people that X >> Y, the
rationale for choosing to use it is degraded or even
nullified altogether.</div>
</div>
</div>
</blockquote>
<div><br>
</div>
<div>So I'll rephrase a question I asked earlier that never
got an answer: if I'm developing a commercial project based
on ghc and some ecosystem, what would possibly cause me to
change either the ghc version or any part of the ecosystem
every other quarter? Or ever, for that matter?</div>
</div>
</div>
</blockquote>
I don't know about them, I can tell you my personal experience.<br>
<br>
If GHC and all libraries were perfect and free from bugs and
ultimately optimized, then you'd be right: there would be no reason
to change.<br>
<br>
But if you ever hit a bug in GHC or a library which was fixed in a
future version, or if you want an improvement made to it, you may
have to update the compiler.<br>
<br>
Library creators/maintainers do not always maintain their libraries
compatible with very old/very new versions of the compiler. In an
ecosystem like ours, with 3 versions of the compiler in use
simultaneously, each with different language features and base APIs
changed, compatibility requires a lot of work.<br>
<br>
This problem is transitive: if you depend on (a new version of a
library that depends on)* a new version of base or a new language
feature, you'll may have to update GHC. If you do not have the
resources to backport those fixes and improvements, you'll be forced
to update. In large projects you are likely to use hundreds of
auxiliary libraries, so this is very likely to happen.<br>
<br>
I recently had to do this for one library because I could only
compile it with a newer version of GHC. This project had 30K lines
of Haskell split in dozens of libraries and a few commercial
projects in production. It meant fixing, recompiling, packaging and
testing everything again, which takes days and it's not unattended
work :( It could easily happen again if I depend on anything that
stops compiling with this version of GHC because someone considers
it "outdated" or does not have the resources to maintain two
versions of his/her library.<br>
<br>
Does that more or less answer your question?<br>
<br>
Cheers<br>
<br>
Ivan<br>
<br>
PS. I do not use stack yet. So, I remain ignorant about that. I see
how it could help in some cases, but not this one.<br>
</body>
</html>