Practice quesitions + solutions SML

[Maloo]

Hey guys,
Does anyone of you know of some resource on the internet with SML
practice questions along with solutions ?
It really helps.

thanks

[TheGist]

In article <espe81$9cp$1...@wolfberry.srv.cs.cmu.edu>,
"Maloo" <ak.u...@gmail.com> wrote:

I would recommend picking up Ullman's book.
http://www.amazon.com/Elements-ML-Programming-ML97-2nd/dp/0137903871
The book is very good and has lots of excercises to try.
Solutions are available from the author's website so you can check your
solutions.

[Chris Reade]

I have some old workshop material containing exercises online (for
beginners and no longer maintained) at
http://www.kingston.ac.uk/~ku07009/MLWorkshop/start.html

Chris Reade

On 8 Mar 2007, at 02:46, Maloo wrote:

> Hey guys,
> Does anyone of you know of some resource on the internet with SML
> practice questions along with solutions ?
> It really helps.
>
> thanks
>
>
>

> This email has been scanned for all viruses by the MessageLabs Email
> Security System.

[John Terrence]

In <et9rnc$6op$1...@wolfberry.srv.cs.cmu.edu> Chris Reade wrote:
> I have some old workshop material containing exercises online (for
> beginners and no longer maintained) at
> http://www.kingston.ac.uk/~ku07009/MLWorkshop/start.html
>
> Chris Reade
> On 8 Mar 2007, at 02:46, Maloo wrote:

Hi Chris Reade !

Sorry to hijack a thread like this, but asked a question about your book
"EFP" in another thread.

fun f1 (x,y,z) = (x,y,1) fun f2 (x,y,z) = (x,y,z * x) fun f3 (x + 1, y,
z) = (x + 1, y, z)
val body = f3.f2

goes crazy on SML-NJ:

Standard ML of New Jersey v110.60 [built: Sun Nov 12 17:21:48 2006]
- [
opening /tmp/sml18216PQH]
/tmp/sml18216PQH:5.5-5.37 Error: non-
constructor applied to argument in pattern: +
/tmp/sml18216PQH:5.25
Error: unbound variable or constructor: x
/tmp/sml18216PQH:6.12-6.17
Error: unbound structure: f3 in path f3.f2
uncaught exception Error

raised at: ../compiler/TopLevel/interact/evalloop.sml:63.48-63.56
../
compiler/TopLevel/interact/evalloop.sml:44.55
../compiler/
TopLevel/interact/evalloop.sml:291.17-291.20
- f2; stdIn:1.1-1.3 Error:
unbound variable or constructor: f2
- f1; stdIn:1.1-1.3 Error: unbound
variable or constructor: f1
- body; stdIn:1.1-1.5 Error: unbound
variable or constructor: body
-

I'm using sml-mode.
Can you help?
Thanks in advance.

JT.

[Chris Reade]

John

In the "EFP" book a small circle is used for composition with an
explanation that this is written as a lower case o in ML (not a dot).
Also the definition in the book is not as you have written it. It
should be:

fun f1 (x,y,z) = (x,y,1)
fun f2 (x,y,z) = (x,y,z * x)

fun f3 (x, y,z) = (x + 1, y, z)
val body = f3 o f2

Chris Reade

[JT]

Chris Reade escreveu:

> John
>
> In the "EFP" book a small circle is used for composition with an
> explanation that this is written as a lower case o in ML (not a dot).
> Also the definition in the book is not as you have written it. It
> should be:
>
> fun f1 (x,y,z) = (x,y,1)
> fun f2 (x,y,z) = (x,y,z * x)
> fun f3 (x, y,z) = (x + 1, y, z)
> val body = f3 o f2
>
> Chris Reade
>

Hi --

Upon evaluating this, an error crops up. I have no idea as to what it
means.

- fun f1 (x,y,z) = (x,y,1);
val f1 = fn : 'a * 'b * 'c -> 'a * 'b * int
- fun f2 (x,y,z) = (x,y,z*x);
val f2 = fn : int * 'a * int -> int * 'a * int
- fun f3 (x,y,z) = (x + 1, y, z);
val f3 = fn : int * 'a * 'b -> int * 'a * 'b
- val body = f3 o f2;
stdIn:5.5-5.19 Warning: type vars not generalized because of
value restriction are instantiated to dummy types (X1,X2,...)
val body = fn : int * ?.X1 * int -> int * ?.X1 * int

This must have something to do with the newer SML 97 standard.
Any help is appreciated.
JT.

[Torben Ægidius Mogensen]

JT <j...@nowherenow.com> writes:

> Chris Reade escreveu:

>> fun f1 (x,y,z) = (x,y,1)
>> fun f2 (x,y,z) = (x,y,z * x)
>> fun f3 (x, y,z) = (x + 1, y, z)
>> val body = f3 o f2

> Upon evaluating this, an error crops up.
>

> - val body = f3 o f2;
> stdIn:5.5-5.19 Warning: type vars not generalized because of
> value restriction are instantiated to dummy types (X1,X2,...)
> val body = fn : int * ?.X1 * int -> int * ?.X1 * int
>
> This must have something to do with the newer SML 97 standard.

It does indeed. SML 97 restricts non-values in val bindings to
monomorphic to avoid problems with polymorphic references. Since the
expression f3 o f2 is not a value, it is not generalized (made
polymorphic). To get around the problem, you can eta-expand the
expression:

val body = fn arg => (f3 o f2) arg

which reduces to

val body = fn arg => f3 (f2 arg)

or, even simpler,

fun body arg = f3 (f2 arg)

Torben