[Builtins] Add the 'dropList' builtin by effectfully · Pull Request #6468 · IntersectMBO/plutus

effectfully · 2024-09-11T18:05:09Z

This experiment adds the dropList builtin so that folks can play with it. Not intended for merging.

…to effectfully/builtins/add-dropList

kwxm

I've added some comments based on a quick look. I may have another look later.

kwxm · 2024-10-30T06:50:02Z

plutus-core/plutus-core/src/PlutusCore/Default/Builtins.hs

            (runCostingFunOneArgument . paramNullList)

+    toBuiltinMeaning _semvar DropList =
+        let dropListDenotation :: Int -> SomeConstant uni [a] -> BuiltinResult (Opaque val [a])


The time taken for this will probably be linear in the value (not the size!) of the first argument. That'll mean using some newtype wrapper, like this . We already have IntegerCostedLiterally, but this has an Int so that may need another wrapper.

^ @ramsay-t FYI

but this has an Int so that may need another wrapper.

Actually, why did I even make it Int, what's the point? Looks like a thinko.

The time taken for this will probably be linear in the value (not the size!) of the first argument.

No, I think it's gonna be a minimum of

linear in the value of the first argument

linear in the length of the second argument

since drop maxBound [] equals [].

Actually, why did I even make it Int, what's the point? Looks like a thinko.

It's proper Integer in there now.

No, I think it's gonna be a minimum of
linear in the value of the first argument
linear in the length of the second argument
since drop maxBound [] equals [].

I deliberately ignored that case! If we include the length of the list in the cost calculation then we'll have to traverse the entire list to measure the length when we're about to calculate the cost, and that'll slow things down. If we just base it on the number of things we want to drop then we'll still get a conservative estimate of the cost, and it'll be faster. Also, if you drop the whole of the list then you've probably done something wrong, and people probably won't submit scripts where that actually happens (or at least not often).

Oh I see. OK, that's clever. Yeah, I think I agree, although I'd perhaps prefer to store lists together with their length, although that'd perhaps slow everything else down. Fair enough!

@ramsay-t ignore what I said and only consider the original comment in this thread.

I'd perhaps prefer to store lists together with their length

I've wondered about doing that in the past (and maybe something similar with Data for instance), but what happens if someone lies about the length of a list in their script? Maybe that could be checked during deserialisation ...

kwxm · 2024-10-30T06:54:26Z

plutus-tx/src/PlutusTx/Builtins.hs

                         , headMaybe
                         , BI.head
                         , BI.tail
+                         , BI.drop


Should this also go in PlutusTx.Prelude? I seem to remember that the contents of that file are kind of random though.

kwxm · 2024-10-30T06:56:11Z

plutus-tx/src/PlutusTx/Builtins/Internal.hs

 chooseList (BuiltinList (_:_)) _ b2 = b2

+{-# OPAQUE drop #-}
+drop :: Integer -> BuiltinList a -> BuiltinList a


Why not dropList? So that it just replaces the Haskell version with minimal effort from the user?

For consistency, we also have head (and not headList) and tail (and not tailList) in this file.

…to effectfully/builtins/add-dropList

effectfully · 2024-11-04T13:11:31Z

/benchmark validation

effectfully · 2024-11-04T16:15:14Z

/benchmark validation

…s far less nice than what I had before :( )

…t' into effectfully/builtins/add-dropList

Adding `dropList` caused the `plutus-ledger-api` tests to fail. This should fix it.

kwxm · 2025-02-04T20:39:11Z

This had become very difficult to merge, so it's been closed in favour of #6817.

effectfully added Do not merge Builtins EXPERIMENT Experiments that we probably don't want to merge labels Sep 11, 2024

effectfully force-pushed the effectfully/builtins/add-dropList branch from 017e9d4 to df4dea7 Compare September 11, 2024 18:10

effectfully added the No Changelog Required Add this to skip the Changelog Check label Sep 11, 2024

effectfully mentioned this pull request Sep 13, 2024

CIP-0132? | New Plutus Builtin DropList cardano-foundation/CIPs#767

Merged

effectfully force-pushed the effectfully/builtins/add-dropList branch from df4dea7 to 7be8e1f Compare September 14, 2024 00:43

effectfully added 2 commits September 14, 2024 03:20

[Builtins] Add the 'dropList' builtin

82b2f45

Merge branch 'master' of https://github.com/input-output-hk/plutus in…

e22a57b

…to effectfully/builtins/add-dropList

effectfully force-pushed the effectfully/builtins/add-dropList branch from 7be8e1f to e22a57b Compare September 14, 2024 03:40

effectfully mentioned this pull request Oct 23, 2024

Investigate adding dropList #6593

Closed

3 tasks

effectfully self-assigned this Oct 29, 2024

Merge branch 'master' of https://github.com/input-output-hk/plutus in…

ad25ce7

…to effectfully/builtins/add-dropList

effectfully temporarily deployed to github-pages October 29, 2024 22:16 — with GitHub Actions Inactive

Add 'DropList' to 'builtinsIntroducedIn'

41ea9b6

effectfully force-pushed the effectfully/builtins/add-dropList branch from 16db02d to 41ea9b6 Compare October 29, 2024 23:43

effectfully temporarily deployed to github-pages October 29, 2024 23:43 — with GitHub Actions Inactive

kwxm reviewed Oct 30, 2024

View reviewed changes

effectfully added 2 commits November 4, 2024 14:10

Implement 'dropList' better

5112e9b

Merge branch 'master' of https://github.com/input-output-hk/plutus in…

442beb4

…to effectfully/builtins/add-dropList

effectfully temporarily deployed to github-pages November 4, 2024 13:10 — with GitHub Actions Inactive

effectfully temporarily deployed to github-pages November 4, 2024 13:11 — with GitHub Actions Inactive

effectfully temporarily deployed to github-pages November 4, 2024 15:38 — with GitHub Actions Inactive

Try a conditional build

e8c0b9d

effectfully force-pushed the effectfully/builtins/add-dropList branch from f999164 to e8c0b9d Compare November 4, 2024 15:56

effectfully temporarily deployed to github-pages November 4, 2024 15:56 — with GitHub Actions Inactive

Remove support for 'dropList' on GHC-8.10

d36d0f8

effectfully temporarily deployed to github-pages November 4, 2024 16:08 — with GitHub Actions Inactive

effectfully and others added 16 commits January 30, 2025 14:34

Try a conditional build

8ad592c

Remove support for 'dropList' on GHC-8.10

d84a7f9

wpi

22f6af5

done

4ce2e19

wip

4e4aa97

wip

95b642b

WIP - Costing

95727a0

Working DropList Benchmark (although the concat and zip combination i…

edc2ec4

…s far less nice than what I had before :( )

Add speculative memory cost model for dropList

2f28c53

Add speculative memory cost model for dropList

25e1a62

Actually typecorrect benchmark...

6839be0

Fixed the memory model file

36bd669

Add dropList benchmark results to cost model

634404d

Remove superfluous comma

a09974e

Merge remote-tracking branch 'origin/effectfully/builtins/add-dropLis…

3780ed0

…t' into effectfully/builtins/add-dropList

[Builtins] Add the 'dropList' builtin

d1cd3a4

ramsay-t temporarily deployed to github-pages January 30, 2025 14:50 — with GitHub Actions Inactive

Fix broken merge

ef65b63

ramsay-t temporarily deployed to github-pages January 31, 2025 08:55 — with GitHub Actions Inactive

Update EvaluationContext.hs

84a478c

Adding `dropList` caused the `plutus-ledger-api` tests to fail. This should fix it.

kwxm temporarily deployed to github-pages January 31, 2025 10:29 — with GitHub Actions Inactive

Update EvaluationContext.hs

9557ae9

Adding `dropList` caused the `plutus-ledger-api` tests to fail. This should fix it.

kwxm temporarily deployed to github-pages January 31, 2025 10:30 — with GitHub Actions Inactive

Fix failing plutus-ledger-api tests

1523fc4

kwxm temporarily deployed to github-pages January 31, 2025 12:09 — with GitHub Actions Inactive

kwxm mentioned this pull request Jan 31, 2025

Add the 'dropList' builtin, take 2 #6817

Merged

kwxm closed this Feb 4, 2025

kwxm deleted the effectfully/builtins/add-dropList branch September 13, 2025 05:05

juloch1 unassigned effectfully Nov 28, 2025

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effectfully commented Sep 11, 2024

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