DynComms [0/n]: `fn` package additions #8653

ProofOfKeags · 2024-04-15T20:41:44Z

NOTE: This change is part of a series implementing Dynamic Commitments.

Change Description

This adds some useful library functions that will allow us to capture patterns we often use throughout the codebase. None of the code in this PR has any direct bearing on Dynamic Commitments but it is generally useful infrastructure that will be assumed to be available in future PRs in the series.

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N/A

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ziggie1984

LGTM, I wonder where you get the inspiration for these library functions, these functions are almost suitable for a general golang library using generics ?

fn/fn.go

ziggie1984 · 2024-04-22T12:30:48Z

fn/slice_test.go

@@ -136,3 +138,48 @@ func TestZipWith(t *testing.T) {
 		z, []bool{false, true, false, false, false},
 	))
 }
+
+func TestPropForEachConcMapIsomorphism(t *testing.T) {


Seems like the TestProp prefix makes sense to be generalized in our docs, as soon as we do prop testing ? So we have a consistent way throughout the codebase ?

Yeah I agree. Our prop testing is pretty sparse at the moment but it's my preferred form of testing.

ok sounds good, will also create property tests next time, they seem to include also the fuzzing component by creating a whole range of input values.

Maybe we can come up with a nice doc guide in the near future what we expect in general from unit tests in the LND codebase.

Yeah what's also nice about them is that it forces you to think more clearly about what the precise requirements of the system are, as opposed to eyeballing a few test cases and hoping that those cases are enough to make reasonable implementations likely. It's a brittle assumption.

fn/slice_test.go

ziggie1984 · 2024-04-22T12:47:25Z

fn/slice_test.go

+		foundIdx := FindIdx(pred, s)
+
+		// onlyVal :: Option[T2[A, B]] -> Option[B]
+		onlyVal := MapOption(func(t2 T2[int, uint8]) uint8 {


wondering if it makes sense to generalize it ?

Generalize what?

mapping a tuple to an Option Tuple to a value: [T2[A, B]] -> Option[T2[A, B]] -> Option[B], could be part of the tuple definition ?

I don't think it should be. However, I do think that maybe exporting functions for Fst and Snd is a good idea.

fn/either.go

ProofOfKeags · 2024-04-22T18:56:11Z

I wonder where you get the inspiration for these library functions, these functions are almost suitable for a general golang library using generics ?

Years of writing Haskell as my native language. Yeah this would be better suited for a golang general lib but I have no desire to do ongoing maintenance of go libraries for the whole golang ecosystem. Further, @Roasbeef doesn't want to depend on external libraries for this kind of thing due to OSS maintainer risk (either malice or just disappearing), which is why we invented the fn package in the first place.

Generally speaking, the fn package is not Bitcoin/Lightning specific in any way. We only want to put stuff in here that is genuinely generic for all sorts or problem domains.

fn/either.go

ziggie1984 · 2024-04-24T14:20:41Z

fn/either_test.go

+
+func TestPropConstructorEliminatorDuality(t *testing.T) {
+	f := func(i int, s string, isRight bool) bool {
+		Len := func(s string) int { return len(s) } // smh


Q: what does the comment mean smh ?

"Shake my head", means disappointment. I was making some commentary about how I couldn't just put len in the field as the type func(string) int even though it would be a sensible thing to be able to do. append has similar issues. Perhaps I should either remove the snarky comment or be more explicit about warning people not to try and refactor it away.

fn/either_test.go

ziggie1984 · 2024-04-24T14:40:07Z

fn/slice_test.go

@@ -136,3 +138,48 @@ func TestZipWith(t *testing.T) {
 		z, []bool{false, true, false, false, false},
 	))
 }
+
+func TestPropForEachConcMapIsomorphism(t *testing.T) {


ok sounds good, will also create property tests next time, they seem to include also the fuzzing component by creating a whole range of input values.

Maybe we can come up with a nice doc guide in the near future what we expect in general from unit tests in the LND codebase.

ziggie1984 · 2024-04-24T14:54:01Z

fn/slice_test.go

+		foundIdx := FindIdx(pred, s)
+
+		// onlyVal :: Option[T2[A, B]] -> Option[B]
+		onlyVal := MapOption(func(t2 T2[int, uint8]) uint8 {


mapping a tuple to an Option Tuple to a value: [T2[A, B]] -> Option[T2[A, B]] -> Option[B], could be part of the tuple definition ?

fn/either.go

yyforyongyu

Will review the following PRs to understand the usage.

fn/t2.go

yyforyongyu · 2024-06-12T08:52:21Z

fn/either.go

 }

 // WhenLeft executes the given function if the Either is left.
 func (e Either[L, R]) WhenLeft(f func(L)) {
-	e.left.WhenSome(f)
+	if !e.isRight {


So there's no feedback when calling these WhenLeft or WhenRight? How do the callers know an effect has been applied to an Either obj or not?

Correct. This function should only be used if we want to conditionally run actions using the inner value on one side. If you need to somehow introspect this value to understand whether the closure was run or not, it's probably better to use ElimEither

yyforyongyu · 2024-06-12T09:05:39Z

fn/fn.go

+	}
+}
+
+// Iden is the lef and right identity of Comp. It is a function that simply


Suggested change

// Iden is the lef and right identity of Comp. It is a function that simply

// Iden is the left and right identity of Comp. It is a function that simply

And would be nice to just name it Identity.

We can do so but I'd like to offer a couple of reasons I chose Iden instead.

We have an 80 column limit. This space is quite scarce and Iden takes 5% of it whereas Identity would take 10%.

Simplicity opts for the names iden and comp instead of identity and compose. Given that it is a well-known Bitcoin project I figured it would provide good intuition

yyforyongyu · 2024-06-12T09:10:33Z

fn/list.go

+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS


Q: what is this license stuff, or why here but not in other places?

I source ripped the golang std List and the BSD License they include stipulates that we have to reproduce the license.

yyforyongyu · 2024-06-12T09:16:34Z

fn/list.go

+
+// List represents a doubly linked list.
+// The zero value for List is an empty list ready to use.
+type List[A any] struct {


hmm there's already lru.List and lru.Cache tho, and we would prefer lru.Cache as it's memory safe.

I couldn't find "List". I did find lru.Cache[K, V any], but I fail to understand precisely how that substitutes here.

Yeah I ripped this in the LRU package for neutrino: https://github.com/lightninglabs/neutrino/blob/master/cache/lru/list.go

yyforyongyu · 2024-06-12T09:22:30Z

fn/slice.go

+		i, a := i, a
+		wait.Add(1)
+		go func() {
+			bs[i] = f(a)


will this create race?

I don't understand how it would given that each thread's landing zone is preallocated and distinct.

yyforyongyu · 2024-06-12T09:22:42Z

fn/slice.go

+	bs := make([]B, len(as))
+
+	for i, a := range as {
+		i, a := i, a


not sure I understand this swap

What swap? I think this is just the required loopvar aliasing because go is strange in this way.

We can drop this safely now (latest Go version).

lightninglabs-deploy · 2024-07-03T23:36:47Z

@yyforyongyu: review reminder
@ProofOfKeags, remember to re-request review from reviewers when ready

Roasbeef · 2024-07-10T21:19:59Z

fn/fn.go

+// argument. This can be a useful utility when taking functions defined in a
+// typical go style and adapting them to work with higher-order functions that
+// expect functions of a single argument.
+func Curry[A, B, C any](f func(A, B) C) func(A) func(B) C {


Could be cut perhaps? Main thing that jumps to mind is syntax bloat, same with Uncurry.

Roasbeef · 2024-07-10T21:20:41Z

fn/slice.go

+	bs := make([]B, len(as))
+
+	for i, a := range as {
+		i, a := i, a


We can drop this safely now (latest Go version).

Roasbeef · 2024-07-10T21:20:59Z

fn/slice.go

+// goroutine for each element in the slice and then awaits all results before
+// returning them.
+func ForEachConc[A, B any](f func(A) B, as []A) []B {
+	wait := sync.WaitGroup{}


Style nit, can just be:

var wait sync.WaitGroup

Roasbeef · 2024-07-10T21:22:11Z

fn/slice.go

+// ForEachConc maps the argument function over the slice, spawning a new
+// goroutine for each element in the slice and then awaits all results before
+// returning them.
+func ForEachConc[A, B any](f func(A) B, as []A) []B {


Perhaps we can lift this version? It uses an errgroup to make it easier to manage error result values: https://github.com/lightninglabs/taproot-assets/blob/main/fn/concurrency.go#L10-L34

Roasbeef · 2024-07-10T21:23:42Z

fn/slice.go

@@ -99,6 +99,18 @@ func Find[A any](pred func(A) bool, s []A) Option[A] {
 	return None[A]()
 }

+// FindIdx returns the first value that passes the supplied predicate along with
+// its index in the slice. If no satisfactory value is found, None is returned.
+func FindIdx[A any](pred func(A) bool, s []A) Option[T2[int, A]] {


Stdlib has this now: https://pkg.go.dev/slices#Index

Could call it, then map the -1 to an option.

Roasbeef · 2024-07-10T21:27:27Z

fn/list.go

+
+// List represents a doubly linked list.
+// The zero value for List is an empty list ready to use.
+type List[A any] struct {


Yeah I ripped this in the LRU package for neutrino: https://github.com/lightninglabs/neutrino/blob/master/cache/lru/list.go

ProofOfKeags force-pushed the fn-prim branch from d0b932b to 41f6492 Compare April 15, 2024 20:49

ProofOfKeags requested review from a team, yyforyongyu and morehouse and removed request for a team April 15, 2024 20:54

ProofOfKeags force-pushed the fn-prim branch from f555c73 to 51298e8 Compare April 16, 2024 17:17

ProofOfKeags added no-changelog no-itest labels Apr 16, 2024

ProofOfKeags self-assigned this Apr 16, 2024

ProofOfKeags added fn llm-review add to a PR to have an LLM bot review it labels Apr 16, 2024

ProofOfKeags requested review from ziggie1984 and removed request for morehouse April 17, 2024 19:04

ProofOfKeags force-pushed the fn-prim branch 2 times, most recently from 464abe1 to 22b714d Compare April 17, 2024 20:18

ProofOfKeags changed the title ~~Add fn tools~~ DynComms [0/n]: fn package additions Apr 17, 2024

ziggie1984 approved these changes Apr 22, 2024

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ProofOfKeags force-pushed the fn-prim branch from df707b0 to 548bf9e Compare April 22, 2024 20:56

ziggie1984 reviewed Apr 24, 2024

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ProofOfKeags force-pushed the fn-prim branch from 548bf9e to 09b6323 Compare April 25, 2024 21:27

saubyk added the dynamic commitments label Apr 30, 2024

saubyk added this to the 0.19.0 milestone Apr 30, 2024

ProofOfKeags force-pushed the fn-prim branch 3 times, most recently from dff47f3 to 728055a Compare April 30, 2024 22:39

ProofOfKeags mentioned this pull request May 14, 2024

[epic]: Dynamic Commitments (Dynamic Channels) #7878

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18 tasks

ProofOfKeags force-pushed the fn-prim branch from 728055a to 0aa7c2a Compare May 14, 2024 19:43

ProofOfKeags force-pushed the fn-prim branch from 0aa7c2a to 07bae01 Compare June 5, 2024 23:27

ProofOfKeags requested a review from guggero June 5, 2024 23:30

ProofOfKeags force-pushed the fn-prim branch 2 times, most recently from 0398ffe to f6f92d6 Compare June 10, 2024 19:23

saubyk removed the request for review from guggero June 11, 2024 04:51

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ProofOfKeags force-pushed the fn-prim branch 3 times, most recently from a5f5c21 to 0a4b0f3 Compare June 12, 2024 23:02

ProofOfKeags requested a review from yyforyongyu June 12, 2024 23:12

ProofOfKeags force-pushed the fn-prim branch from 0a4b0f3 to e01d2d6 Compare June 15, 2024 00:58

ProofOfKeags force-pushed the fn-prim branch from e01d2d6 to 60a97b3 Compare June 28, 2024 22:14

ProofOfKeags added 8 commits July 8, 2024 14:19

fn: add fundamental functional primitives

6f96721

fn: add concurrent map operation for slices

0dfa754

fn: add FindIdx function

0afb935

fn: fix and finish the either API

928a2f4

fn: reimplement internals of either, add tests

057166f

fn: add curried (in)equality functions

8373a99

fn: add Elem function for set membership

e87c0ba

fn: add generic version of List

e1bcf04

ProofOfKeags force-pushed the fn-prim branch from 60a97b3 to e1bcf04 Compare July 8, 2024 21:24

Roasbeef reviewed Jul 10, 2024

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	// Iden is the lef and right identity of Comp. It is a function that simply
	// Iden is the left and right identity of Comp. It is a function that simply

DynComms [0/n]: fn package additions #8653

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ProofOfKeags commented Apr 15, 2024 • edited Loading

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DynComms [0/n]: `fn` package additions #8653

DynComms [0/n]: `fn` package additions #8653

ProofOfKeags commented Apr 15, 2024 •

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