Generalizing some type signatures involving Int

newer
Re: Proposal: Num instance for (a...

older
Proposal: Num instance for (a -> b)

Vanessa McHale

13 Nov 2018 13 Nov '18

8:18 p.m.

Would it be possible to generalize replicate and length to have type signatures replicate :: Integral a => a -> b -> [b] and length :: (Integral a, Foldable t) => t b -> a ? There have been a few instances where such a thing would have been useful to me. Cheers

Attachments:

signature.asc (application/pgp-signature — 488 bytes)

Show replies by date

Alexandre Rodrigues

13 Nov 13 Nov

8:34 p.m.

:+1: from me. ________________________________ From: Libraries on behalf of Vanessa McHale Sent: Wednesday, November 14, 2018 1:18:58 AM To: Haskell Libraries Subject: Generalizing some type signatures involving Int Would it be possible to generalize replicate and length to have type signatures replicate :: Integral a => a -> b -> [b] and length :: (Integral a, Foldable t) => t b -> a ? There have been a few instances where such a thing would have been useful to me. Cheers

Eric Mertens

9:49 p.m.

Int is the right type to be able to do efficient internal operations when implementing length and replicate. It's unlikely that someone would want to run these operations on another type internally than Int. Some times people propose types like these where they imagine just a built-in use of fromIntegral on either the initial argument or the result, but that really quite unnecessary. Could you elaborate on what cases you had in mind? While genericLength exists, I have yet to see a good use of it. Best regards, Eric Mertens glguy On Tue, Nov 13, 2018 at 5:34 PM Alexandre Rodrigues < alexandreR_B@outlook.com> wrote:

...

:+1: from me.

------------------------------ *From:* Libraries on behalf of Vanessa McHale *Sent:* Wednesday, November 14, 2018 1:18:58 AM *To:* Haskell Libraries *Subject:* Generalizing some type signatures involving Int

Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

-- Eric Mertens

Vanessa McHale

10:19 p.m.

I certainly do! What's wrong with iterating over a Word? On 11/13/18 8:49 PM, Eric Mertens wrote:

...

Int is the right type to be able to do efficient internal operations when implementing length and replicate. It's unlikely that someone would want to run these operations on another type internally than Int. Some times people propose types like these where they imagine just a built-in use of fromIntegral on either the initial argument or the result, but that really quite unnecessary. Could you elaborate on what cases you had in mind?

While genericLength exists, I have yet to see a good use of it.

Best regards, Eric Mertens glguy

On Tue, Nov 13, 2018 at 5:34 PM Alexandre Rodrigues mailto:alexandreR_B@outlook.com> wrote:

:+1: from me.

------------------------------------------------------------------------ *From:* Libraries mailto:libraries-bounces@haskell.org> on behalf of Vanessa McHale mailto:vanessa.mchale@iohk.io> *Sent:* Wednesday, November 14, 2018 1:18:58 AM *To:* Haskell Libraries *Subject:* Generalizing some type signatures involving Int Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

-- Eric Mertens

Evan Laforge

9:50 p.m.

You can already get these as Data.List.genericLength and Data.List.genericReplicate As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...

Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

David Feuer

10:13 p.m.

genericLength is extremely inefficient for typical numeric types. Int is a rather sad type for these things; it really should be Word. But that may not be worth fixing. On Tue, Nov 13, 2018, 9:51 PM Evan Laforge

...

You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Vanessa McHale

10:24 p.m.

This is perhaps not the right place, but if there are benchmarks proving that genericLength is slower than it should be, it should be easy to add a SPECIALIZE pragma. On 11/13/18 9:13 PM, David Feuer wrote:

...

genericLength is extremely inefficient for typical numeric types. Int is a rather sad type for these things; it really should be Word. But that may not be worth fixing.

On Tue, Nov 13, 2018, 9:51 PM Evan Laforge mailto:qdunkan@gmail.com wrote:

You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale mailto:vanessa.mchale@iohk.io> wrote: > > Would it be possible to generalize replicate and length to have type > signatures > > replicate :: Integral a => a -> b -> [b] > > and > > length :: (Integral a, Foldable t) => t b -> a > > ? > > There have been a few instances where such a thing would have been > useful to me. > > Cheers > > > _______________________________________________ > Libraries mailing list > Libraries@haskell.org mailto:Libraries@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

David Feuer

10:30 p.m.

That won't help whatsoever in most cases. The matter has been discussed several times with no progress. If you want to add RULES for Int8, Int16, ..., Word, Word8, ..., and Natural to match the ones for Int and Integer, that would make sense, but the basic problem will remain for unmentioned types. On Tue, Nov 13, 2018, 10:24 PM Vanessa McHale

...

This is perhaps not the right place, but if there are benchmarks proving that genericLength is slower than it should be, it should be easy to add a SPECIALIZE pragma. On 11/13/18 9:13 PM, David Feuer wrote:

genericLength is extremely inefficient for typical numeric types. Int is a rather sad type for these things; it really should be Word. But that may not be worth fixing.

On Tue, Nov 13, 2018, 9:51 PM Evan Laforge
...
You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Alexandre Rodrigues

14 Nov 14 Nov

1:04 p.m.

I spoke too soon, I failed to consider that such a proposal must have been under consideration many times before, and there must have been a good reason for it to not to move forward. Adding RULES for the most commonly used integer types is probably a good place to start, but perhaps I am mistaken. ________________________________ From: Libraries on behalf of David Feuer Sent: Wednesday, November 14, 2018 3:30:38 AM To: Vanessa McHale Cc: Haskell Libraries Subject: Re: Generalizing some type signatures involving Int That won't help whatsoever in most cases. The matter has been discussed several times with no progress. If you want to add RULES for Int8, Int16, ..., Word, Word8, ..., and Natural to match the ones for Int and Integer, that would make sense, but the basic problem will remain for unmentioned types. On Tue, Nov 13, 2018, 10:24 PM Vanessa McHale mailto:vanessa.mchale@iohk.io wrote: This is perhaps not the right place, but if there are benchmarks proving that genericLength is slower than it should be, it should be easy to add a SPECIALIZE pragma. On 11/13/18 9:13 PM, David Feuer wrote: genericLength is extremely inefficient for typical numeric types. Int is a rather sad type for these things; it really should be Word. But that may not be worth fixing. On Tue, Nov 13, 2018, 9:51 PM Evan Laforge mailto:qdunkan@gmail.com wrote: You can already get these as Data.List.genericLength and Data.List.genericReplicate As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale mailto:vanessa.mchale@iohk.io> wrote:

...

Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.orgmailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.orgmailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Carter Schonwald

15 Nov 15 Nov

1:30 a.m.

Agreed. As David and Eric both say: For in heap / memory size structures, it’s impossible to ever have an in ram structure that exceeds the largest positive value for Int. And ghc is also quite good at optimizing int. 1) what is your application domain / context ? 2) all of these are implementable in user space, what design / implementation experiments have you done ? It’s worth mentioning that RULES style optimization in this case would only run AFTER it’s been specialized to a concrete type. And that short of lots of specialize pragmas or inlining , the generic code will thusly miss out on all sorts of unboxong etc. On Tue, Nov 13, 2018 at 10:31 PM David Feuer wrote:

...

That won't help whatsoever in most cases. The matter has been discussed several times with no progress. If you want to add RULES for Int8, Int16, ..., Word, Word8, ..., and Natural to match the ones for Int and Integer, that would make sense, but the basic problem will remain for unmentioned types.

On Tue, Nov 13, 2018, 10:24 PM Vanessa McHale
...
This is perhaps not the right place, but if there are benchmarks proving that genericLength is slower than it should be, it should be easy to add a SPECIALIZE pragma. On 11/13/18 9:13 PM, David Feuer wrote:

genericLength is extremely inefficient for typical numeric types. Int is a rather sad type for these things; it really should be Word. But that may not be worth fixing.

On Tue, Nov 13, 2018, 9:51 PM Evan Laforge
...
You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Zemyla

5:57 p.m.

It's not actually impossible to have an in RAM structure that exceeds the largest positive value for Int. Data.Sequence.replicate does it by exploiting sharing. replicate n a uses O(lg n) space.

...

length $ let x = Data.Sequence.Replicate maxBound 'a' :> 'b' in mappend x x 0

Also, I really would like to have all the length and count-based functions in base, containers, etc. take or return Words, but there's way too much inertia behind Ints, even if it means you have to check for negative numbers (which really runs counter to the main thesis behind Haskell; i.e. have your types say what you mean). On Thu, Nov 15, 2018 at 12:30 AM Carter Schonwald wrote:

...

Agreed.

As David and Eric both say: For in heap / memory size structures, it’s impossible to ever have an in ram structure that exceeds the largest positive value for Int. And ghc is also quite good at optimizing int.

1) what is your application domain / context ?

2) all of these are implementable in user space, what design / implementation experiments have you done ?

It’s worth mentioning that RULES style optimization in this case would only run AFTER it’s been specialized to a concrete type. And that short of lots of specialize pragmas or inlining , the generic code will thusly miss out on all sorts of unboxong etc.

On Tue, Nov 13, 2018 at 10:31 PM David Feuer wrote:

...
That won't help whatsoever in most cases. The matter has been discussed several times with no progress. If you want to add RULES for Int8, Int16, ..., Word, Word8, ..., and Natural to match the ones for Int and Integer, that would make sense, but the basic problem will remain for unmentioned types.

On Tue, Nov 13, 2018, 10:24 PM Vanessa McHale
...
This is perhaps not the right place, but if there are benchmarks proving that genericLength is slower than it should be, it should be easy to add a SPECIALIZE pragma.

On 11/13/18 9:13 PM, David Feuer wrote:

genericLength is extremely inefficient for typical numeric types. Int is a rather sad type for these things; it really should be Word. But that may not be worth fixing.

On Tue, Nov 13, 2018, 9:51 PM Evan Laforge
...
You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Henning Thielemann

6:18 p.m.

On Thu, 15 Nov 2018, Zemyla wrote:

...

It's not actually impossible to have an in RAM structure that exceeds the largest positive value for Int. Data.Sequence.replicate does it by exploiting sharing. replicate n a uses O(lg n) space.

...
length $ let x = Data.Sequence.Replicate maxBound 'a' :> 'b' in mappend x x 0

One could also imagine a data structure like Multiset/Bag, where every element has a count and 'length' returns the total count.

...

Also, I really would like to have all the length and count-based functions in base, containers, etc. take or return Words, but there's way too much inertia behind Ints, even if it means you have to check for negative numbers (which really runs counter to the main thesis behind Haskell; i.e. have your types say what you mean).

We would also need a bound-checked counterpart to Word. Currently, (-1)::Word or (2-3)::Word is accepted without a runtime error. Consequently, 'newTake (-1) xs' would likely return the full list xs.

David Feuer

9:48 p.m.

Data.Sequence actually doesn't support anything outside the Int range. It could, at a small cost. We perform some range checks cheaply using unsigned comparisons. We'd have to stop doing that to allow sequences to be just a tad more absurdly large. Since that's not often useful, sequences are currently limited to lengths of maxBound @Int. On Thu, Nov 15, 2018, 5:53 PM Zemyla

...

It's not actually impossible to have an in RAM structure that exceeds the largest positive value for Int. Data.Sequence.replicate does it by exploiting sharing. replicate n a uses O(lg n) space.

...
length $ let x = Data.Sequence.Replicate maxBound 'a' :> 'b' in mappend x x 0

Also, I really would like to have all the length and count-based functions in base, containers, etc. take or return Words, but there's way too much inertia behind Ints, even if it means you have to check for negative numbers (which really runs counter to the main thesis behind Haskell; i.e. have your types say what you mean).

On Thu, Nov 15, 2018 at 12:30 AM Carter Schonwald wrote:

...
Agreed.

As David and Eric both say: For in heap / memory size structures, it’s impossible to ever have an in

ram structure that exceeds the largest positive value for Int. And ghc is also quite good at optimizing int.

...
1) what is your application domain / context ?

2) all of these are implementable in user space, what design /

implementation experiments have you done ?

...
It’s worth mentioning that RULES style optimization in this case would

only run AFTER it’s been specialized to a concrete type. And that short of lots of specialize pragmas or inlining , the generic code will thusly miss out on all sorts of unboxong etc.

...
On Tue, Nov 13, 2018 at 10:31 PM David Feuer

...
...
That won't help whatsoever in most cases. The matter has been discussed

several times with no progress. If you want to add RULES for Int8, Int16, ..., Word, Word8, ..., and Natural to match the ones for Int and Integer,

...
...
On Tue, Nov 13, 2018, 10:24 PM Vanessa McHale
wrote:

...
...
This is perhaps not the right place, but if there are benchmarks

wrote: that would make sense, but the basic problem will remain for unmentioned types. proving that genericLength is slower than it should be, it should be easy to add a SPECIALIZE pragma.

...
...
...
On 11/13/18 9:13 PM, David Feuer wrote:

genericLength is extremely inefficient for typical numeric types. Int

is a rather sad type for these things; it really should be Word. But that may not be worth fixing.

...
On Tue, Nov 13, 2018, 9:51 PM Evan Laforge
...
You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale <

vanessa.mchale@iohk.io> wrote:

...
...
...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Vanessa McHale

13 Nov 13 Nov

10:21 p.m.

Thanks! This is a decent stopgap. On 11/13/18 8:50 PM, Evan Laforge wrote:

...

You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

David Feuer

10:22 p.m.

No, genericLength is *not* a decent stopgap. It's horrible. Just look at the implementation! On Tue, Nov 13, 2018, 10:21 PM Vanessa McHale

...

Thanks! This is a decent stopgap.

On 11/13/18 8:50 PM, Evan Laforge wrote:

...
You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Henning Thielemann

15 Nov 15 Nov

1:39 p.m.

On Tue, 13 Nov 2018, David Feuer wrote:

...

No, genericLength is *not* a decent stopgap. It's horrible. Just look at the implementation!

It looks like it is intended to return something like a lazy Peano number.

David Feuer

2:28 p.m.

That is precisely correct. And I have heard that it has actually been used that way ... once. It's not exactly a common application. On Thu, Nov 15, 2018 at 1:39 PM Henning Thielemann wrote:

...

On Tue, 13 Nov 2018, David Feuer wrote:

...
No, genericLength is *not* a decent stopgap. It's horrible. Just look at the implementation!

It looks like it is intended to return something like a lazy Peano number.

Vanessa McHale

13 Nov 13 Nov

10:22 p.m.

I want more than this, actually. genericLength doesn't work over any Foldable. On 11/13/18 8:50 PM, Evan Laforge wrote:

...

You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

David Feuer

10:25 p.m.

You still haven't said why you need this. Only a rather exotic data structure is likely to have a length greater than maxBound @Int. On Tue, Nov 13, 2018, 10:23 PM Vanessa McHale

...

I want more than this, actually. genericLength doesn't work over any Foldable.

On 11/13/18 8:50 PM, Evan Laforge wrote:

...
You can already get these as Data.List.genericLength and Data.List.genericReplicate

As for changing the prelude ones, this would probably cause a lot of busywork. Where I work we compile with -Werror and -Wtype-defaults, so a lot of places might have to get type annotations. On Tue, Nov 13, 2018 at 5:19 PM Vanessa McHale wrote:

...
Would it be possible to generalize replicate and length to have type signatures

replicate :: Integral a => a -> b -> [b]

and

length :: (Integral a, Foldable t) => t b -> a

?

There have been a few instances where such a thing would have been useful to me.

Cheers

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

2377

Age (days ago)

2379

Last active (days ago)

List overview

Download

18 comments

8 participants

participants (8)

Alexandre Rodrigues
Carter Schonwald
David Feuer
Eric Mertens
Evan Laforge
Henning Thielemann
Vanessa McHale
Zemyla

Generalizing some type signatures involving Int

tags

participants (8)