What does '_a mean?
"Douglas Lewit [email protected] [ocaml_beginners]" <[email protected]> Sun, 7 May 2017 01:37:00 -0500
| Newsgroups | gmane.comp.lang.ocaml.beginners |
|---|---|
| Message-ID | <CAM0XMJRr=V9OQeLxsYfnVRqF5UbakEjZkJFMseZhV7HL_B_uRA@mail.gmail.com> |
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Hi everyone,
Right now I'm wrapping up Programming Languages, Part A with Dan Grossman
on Coursera. Great course! The language we're using is Standard ML, which
looks very similar to OCaml. It's an excellent course and I've learned so
much. I strongly recommend it.
Anyhow, I was playing around with OCaml this evening using the utop
environment in my Terminal and noticed something rather interesting. I'm
accustomed to the 'a or 'b or 'c type. But I noticed this evening an
unusual notation.... what is '_a? How is *'_a* different from *'a*? I'm
using OCaml, version 4.04, which I think is the latest version of the
language. Is this something new that OCaml's developers have decided to
introduce into the language? I would be very grateful if someone can
provide a simple explanation of what this is and why it's important.
Just as a side note, does anyone have any opinions about SML? I like the
language a lot, although I think OCaml does a much better job of
implementing non-tail recursive functions than SML. But how much stack
memory is available to a language's compiler or interpreter is probably
more of an implementation issue than a true language issue.
I appreciate the feedback.
Thanks,
Douglas Lewit
P.S. Does someone know how to turn off Warning 8, the warning about
non-exhaustive pattern matching? The compiler returned Warning 8 about one
of my functions, but the function works exactly the way I want it to, so I
don't really see what the problem is.
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<p><div dir=3D"ltr"><font size=3D"4">Hi everyone,</font><div><font si=
ze=3D"4"><br></font></div><div><font size=3D"4">Right now I'm wrapping =
up Programming Languages, Part A with Dan Grossman on Coursera.=C2=A0 Great=
course!=C2=A0 The language we're using is Standard ML, which looks ver=
y similar to OCaml.=C2=A0 It's an excellent course and I've learned=
so much.=C2=A0 I strongly recommend it. =C2=A0</font></div><div><font size=
=3D"4"><br></font></div><div><font size=3D"4">Anyhow, I was playing around =
with OCaml this evening using the utop environment in my Terminal and notic=
ed something rather interesting.=C2=A0 I'm accustomed to the 'a or =
'b or 'c type.=C2=A0 But I noticed this evening an unusual notation=
.... what is '_a?=C2=A0 How is <b>'_a</b> different from <b>'a<=
/b>?=C2=A0 I'm using OCaml, version 4.04, which I think is the latest v=
ersion of the language.=C2=A0 Is this something new that OCaml's develo=
pers have decided to introduce into the language?=C2=A0 I would be very gra=
teful if someone can provide a simple explanation of what this is and why i=
t's important.</font></div><div><font size=3D"4"><br></font></div><div>=
<font size=3D"4">Just as a side note, does anyone have any opinions about S=
ML?=C2=A0 I like the language a lot, although I think OCaml does a much bet=
ter job of implementing non-tail recursive functions than SML.=C2=A0 But ho=
w much stack memory is available to a language's compiler or interprete=
r is probably more of an implementation issue than a true language issue.</=
font></div><div><font size=3D"4"><br></font></div><div><font size=3D"4">I a=
ppreciate the feedback.</font></div><div><font size=3D"4"><br></font></div>=
<div><font size=3D"4">Thanks,</font></div><div><font size=3D"4"><br></font>=
</div><div><font size=3D"4">Douglas Lewit</font></div><div><font size=3D"4"=
><br></font></div><div><font size=3D"4">P.S.=C2=A0 Does someone know how to=
turn off Warning 8, the warning about non-exhaustive pattern matching?=C2=
=A0 The compiler returned Warning 8 about one of my functions, but the func=
tion works exactly the way I want it to, so I don't really see what the=
problem is.</font></div><div><font size=3D"4"><br></font></div></div>
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