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@rvanasa rvanasa commented Jan 27, 2026

Resolves an API inconsistency between Array and other data structures, motivated by Array.contains being commonly hallucinated by Caffeine / LLMs.

@rvanasa rvanasa requested a review from a team as a code owner January 27, 2026 15:35
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Benchmark Results

bench/ArrayBuilding.bench.mo $({\color{green}-0.20\%})$

Large known-size array building

Compares performance of different data structures for building arrays of known size.

Instructions: ${\color{green}-0.14\%}$
Heap: ${\color{gray}0\%}$
Stable Memory: ${\color{gray}0\%}$
Garbage Collection: ${\color{green}-0.05\%}$

Instructions

1000 100000 1000000
List 542_131 $({\color{green}-1.11\%})$ 47_994_607 $({\color{green}-0.68\%})$ 475_069_659 $({\color{green}-0.65\%})$
Buffer 341_989 $({\color{green}-0.00\%})$ 33_903_411 $({\color{green}-0.00\%})$ 339_003_622 $({\color{green}-0.00\%})$
pure/List 302_119 $({\color{green}-0.01\%})$ 30_003_566 $({\color{green}-0.00\%})$ 300_055_944 $({\color{green}-0.00\%})$
VarArray ?T 180_502 $({\color{green}-0.01\%})$ 17_802_924 $({\color{green}-0.00\%})$ 178_003_135 $({\color{green}-0.00\%})$
VarArray T 160_797 $({\color{green}-0.01\%})$ 15_803_219 $({\color{green}-0.00\%})$ 158_003_430 $({\color{green}-0.00\%})$
Array (baseline) 42_671 $({\color{green}-0.06\%})$ 4_003_093 $({\color{green}-0.00\%})$ 40_003_304 $({\color{green}-0.00\%})$

Heap

1000 100000 1000000
List 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
Buffer 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
pure/List 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
VarArray ?T 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
VarArray T 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
Array (baseline) 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$

Garbage Collection

1000 100000 1000000
List 9.96 KiB $({\color{green}-0.97\%})$ 797.46 KiB $({\color{green}-0.01\%})$ 7.67 MiB $({\color{green}-0.00\%})$
Buffer 8.71 KiB $({\color{gray}0\%})$ 782.15 KiB $({\color{gray}0\%})$ 7.63 MiB $({\color{gray}0\%})$
pure/List 19.95 KiB $({\color{gray}0\%})$ 1.91 MiB $({\color{gray}0\%})$ 19.07 MiB $({\color{gray}0\%})$
VarArray ?T 8.24 KiB $({\color{gray}0\%})$ 781.68 KiB $({\color{gray}0\%})$ 7.63 MiB $({\color{gray}0\%})$
VarArray T 8.23 KiB $({\color{gray}0\%})$ 781.67 KiB $({\color{gray}0\%})$ 7.63 MiB $({\color{gray}0\%})$
Array (baseline) 4.3 KiB $({\color{gray}0\%})$ 391.02 KiB $({\color{gray}0\%})$ 3.82 MiB $({\color{gray}0\%})$
bench/FromIters.bench.mo $({\color{green}-0.00\%})$

Benchmarking the fromIter functions

Columns describe the number of elements in the input iter.

Instructions: ${\color{green}-0.00\%}$
Heap: ${\color{gray}0\%}$
Stable Memory: ${\color{gray}0\%}$
Garbage Collection: ${\color{gray}0\%}$

Instructions

100 10_000 100_000
Array.fromIter 48_764 $({\color{gray}0\%})$ 4_712_025 $({\color{gray}0\%})$ 47_103_133 $({\color{green}-0.00\%})$
List.fromIter 31_698 $({\color{gray}0\%})$ 3_061_541 $({\color{gray}0\%})$ 30_603_551 $({\color{green}-0.00\%})$
List.fromIter . Iter.reverse 50_295 $({\color{green}-0.00\%})$ 4_832_561 $({\color{green}-0.00\%})$ 48_305_473 $({\color{green}-0.00\%})$

Heap

100 10_000 100_000
Array.fromIter 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
List.fromIter 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
List.fromIter . Iter.reverse 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$

Garbage Collection

100 10_000 100_000
Array.fromIter 2.76 KiB $({\color{gray}0\%})$ 234.79 KiB $({\color{gray}0\%})$ 2.29 MiB $({\color{gray}0\%})$
List.fromIter 3.51 KiB $({\color{gray}0\%})$ 312.88 KiB $({\color{gray}0\%})$ 3.05 MiB $({\color{gray}0\%})$
List.fromIter . Iter.reverse 5.11 KiB $({\color{gray}0\%})$ 469.17 KiB $({\color{gray}0\%})$ 4.58 MiB $({\color{gray}0\%})$
bench/ListBufferNewArray.bench.mo $({\color{green}-6.13\%})$

List vs. Buffer for creating known-size arrays

Performance comparison between List and Buffer for creating a new array.

Instructions: ${\color{green}-1.95\%}$
Heap: ${\color{gray}0\%}$
Stable Memory: ${\color{gray}0\%}$
Garbage Collection: ${\color{green}-4.19\%}$

Instructions

0 (baseline) 1 5 10 100 (for loop)
List 1_367 $({\color{green}-11.64\%})$ 2_687 $({\color{green}-7.85\%})$ 8_667 $({\color{green}-4.19\%})$ 13_460 $({\color{green}-3.50\%})$ 73_160 $({\color{green}-1.88\%})$
pure/List 1_247 $({\color{gray}0\%})$ 1_355 $({\color{gray}0\%})$ 2_439 $({\color{gray}0\%})$ 3_799 $({\color{green}-0.05\%})$ 31_864 $({\color{green}-0.01\%})$
Buffer 2_119 $({\color{gray}0\%})$ 2_271 $({\color{gray}0\%})$ 3_518 $({\color{gray}0\%})$ 5_083 $({\color{green}-0.04\%})$ 36_636 $({\color{green}-0.01\%})$

Heap

0 (baseline) 1 5 10 100 (for loop)
List 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
pure/List 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
Buffer 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$

Garbage Collection

0 (baseline) 1 5 10 100 (for loop)
List 476 B $({\color{green}-17.36\%})$ 516 B $({\color{green}-16.23\%})$ 676 B $({\color{green}-12.89\%})$ 784 B $({\color{green}-11.31\%})$ 1.84 KiB $({\color{green}-5.05\%})$
pure/List 360 B $({\color{gray}0\%})$ 380 B $({\color{gray}0\%})$ 460 B $({\color{gray}0\%})$ 560 B $({\color{gray}0\%})$ 2.3 KiB $({\color{gray}0\%})$
Buffer 856 B $({\color{gray}0\%})$ 864 B $({\color{gray}0\%})$ 896 B $({\color{gray}0\%})$ 936 B $({\color{gray}0\%})$ 1.62 KiB $({\color{gray}0\%})$
bench/PriorityQueues.bench.mo $({\color{green}-2.68\%})$

Different priority queue implementations

_Compare the performance of the following priority queue implementations:

  • PriorityQueue: Binary heap implementation over List.
  • PriorityQueueSet: Wrapper over Set<(T, Nat)>._

Instructions: ${\color{green}-2.70\%}$
Heap: ${\color{gray}0\%}$
Stable Memory: ${\color{gray}0\%}$
Garbage Collection: ${\color{red}+0.02\%}$

Instructions

A) PriorityQueue B) PriorityQueueSet
1.) 100000 operations (push:pop = 1:1) 568_913_098 $({\color{green}-4.79\%})$ 522_729_615 $({\color{green}-0.00\%})$
2.) 100000 operations (push:pop = 2:1) 707_495_219 $({\color{green}-4.77\%})$ 809_692_923 $({\color{green}-0.00\%})$
3.) 100000 operations (push:pop = 10:1) 336_409_742 $({\color{green}-6.01\%})$ 873_180_905 $({\color{green}-0.00\%})$
4.) 100000 operations (only push) 176_982_954 $({\color{green}-8.02\%})$ 886_824_587 $({\color{green}-0.00\%})$
5.) 50000 pushes, then 50000 pops 745_226_697 $({\color{green}-4.04\%})$ 961_778_010 $({\color{red}+0.00\%})$
6.) 50000 pushes, then 25000 "pop;push"es 504_254_187 $({\color{green}-4.76\%})$ 922_136_291 $({\color{green}-0.00\%})$

Heap

A) PriorityQueue B) PriorityQueueSet
1.) 100000 operations (push:pop = 1:1) 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
2.) 100000 operations (push:pop = 2:1) 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
3.) 100000 operations (push:pop = 10:1) 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
4.) 100000 operations (only push) 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
5.) 50000 pushes, then 50000 pops 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$
6.) 50000 pushes, then 25000 "pop;push"es 272 B $({\color{gray}0\%})$ 272 B $({\color{gray}0\%})$

Garbage Collection

A) PriorityQueue B) PriorityQueueSet
1.) 100000 operations (push:pop = 1:1) 15.07 MiB $({\color{red}+0.24\%})$ 17.43 MiB $({\color{gray}0\%})$
2.) 100000 operations (push:pop = 2:1) 19.73 MiB $({\color{gray}0\%})$ 19.32 MiB $({\color{gray}0\%})$
3.) 100000 operations (push:pop = 10:1) 8.67 MiB $({\color{gray}0\%})$ 12.64 MiB $({\color{gray}0\%})$
4.) 100000 operations (only push) 3.87 MiB $({\color{gray}0\%})$ 9.96 MiB $({\color{gray}0\%})$
5.) 50000 pushes, then 50000 pops 22.03 MiB $({\color{red}+0.02\%})$ 26.2 MiB $({\color{gray}0\%})$
6.) 50000 pushes, then 25000 "pop;push"es 14.22 MiB $({\color{gray}0\%})$ 18.44 MiB $({\color{gray}0\%})$
bench/PureListStackSafety.bench.mo $({\color{green}-0.00\%})$

List Stack safety

Check stack-safety of the following pure/List-related functions.

Instructions: ${\color{green}-0.00\%}$
Heap: ${\color{gray}0\%}$
Stable Memory: ${\color{gray}0\%}$
Garbage Collection: ${\color{gray}0\%}$

Instructions

pure/List.split 24_602_524 $({\color{gray}0\%})$
pure/List.all 7_901_014 $({\color{gray}0\%})$
pure/List.any 8_001_390 $({\color{gray}0\%})$
pure/List.map 23_103_767 $({\color{gray}0\%})$
pure/List.filter 21_104_188 $({\color{gray}0\%})$
pure/List.filterMap 27_404_740 $({\color{green}-0.00\%})$
pure/List.partition 21_304_994 $({\color{gray}0\%})$
pure/List.join 33_105_326 $({\color{gray}0\%})$
pure/List.flatten 24_805_667 $({\color{gray}0\%})$
pure/List.take 24_605_664 $({\color{gray}0\%})$
pure/List.drop 9_904_119 $({\color{gray}0\%})$
pure/List.foldRight 19_105_768 $({\color{gray}0\%})$
pure/List.merge 31_808_584 $({\color{gray}0\%})$
pure/List.chunks 51_510_344 $({\color{gray}0\%})$
pure/Queue 142_662_505 $({\color{gray}0\%})$

Heap

pure/List.split 272 B $({\color{gray}0\%})$
pure/List.all 272 B $({\color{gray}0\%})$
pure/List.any 272 B $({\color{gray}0\%})$
pure/List.map 272 B $({\color{gray}0\%})$
pure/List.filter 272 B $({\color{gray}0\%})$
pure/List.filterMap 272 B $({\color{gray}0\%})$
pure/List.partition 272 B $({\color{gray}0\%})$
pure/List.join 272 B $({\color{gray}0\%})$
pure/List.flatten 272 B $({\color{gray}0\%})$
pure/List.take 272 B $({\color{gray}0\%})$
pure/List.drop 272 B $({\color{gray}0\%})$
pure/List.foldRight 272 B $({\color{gray}0\%})$
pure/List.merge 272 B $({\color{gray}0\%})$
pure/List.chunks 272 B $({\color{gray}0\%})$
pure/Queue 272 B $({\color{gray}0\%})$

Garbage Collection

pure/List.split 3.05 MiB $({\color{gray}0\%})$
pure/List.all 328 B $({\color{gray}0\%})$
pure/List.any 328 B $({\color{gray}0\%})$
pure/List.map 3.05 MiB $({\color{gray}0\%})$
pure/List.filter 3.05 MiB $({\color{gray}0\%})$
pure/List.filterMap 3.05 MiB $({\color{gray}0\%})$
pure/List.partition 3.05 MiB $({\color{gray}0\%})$
pure/List.join 3.05 MiB $({\color{gray}0\%})$
pure/List.flatten 3.05 MiB $({\color{gray}0\%})$
pure/List.take 3.05 MiB $({\color{gray}0\%})$
pure/List.drop 328 B $({\color{gray}0\%})$
pure/List.foldRight 1.53 MiB $({\color{gray}0\%})$
pure/List.merge 4.58 MiB $({\color{gray}0\%})$
pure/List.chunks 7.63 MiB $({\color{gray}0\%})$
pure/Queue 18.31 MiB $({\color{gray}0\%})$
bench/Queues.bench.mo $({\color{red}+0.00\%})$

Different queue implementations

Compare the performance of the following queue implementations:

  • pure/Queue: The default immutable double-ended queue implementation.
    • Pros: Good amortized performance, meaning that the average cost of operations is low O(1).
    • Cons: In worst case, an operation can take O(size) time rebuilding the queue as demonstrated in the Pop front 2 elements scenario.
  • pure/RealTimeQueue
    • Pros: Every operation is guaranteed to take at most O(1) time and space.
    • Cons: Poor amortized performance: Instruction cost is on average 3x for pop and 8x for push compared to pure/Queue.
  • mutable Queue
    • Pros: Also O(1) guarantees with a lower constant factor than pure/RealTimeQueue. Amortized performance is comparable to pure/Queue.
    • Cons: It is mutable and cannot be used in shared types (not shareable).

Instructions: ${\color{red}+0.00\%}$
Heap: ${\color{gray}0\%}$
Stable Memory: ${\color{gray}0\%}$
Garbage Collection: ${\color{gray}0\%}$

Instructions

pure/Queue pure/RealTimeQueue mutable Queue
Initialize with 2 elements 3_092 $({\color{gray}0\%})$ 2_304 $({\color{gray}0\%})$ 3_040 $({\color{gray}0\%})$
Push 500 elements 90_713 $({\color{gray}0\%})$ 744_219 $({\color{gray}0\%})$ 219_325 $({\color{red}+0.02\%})$
Pop front 2 elements 86_966 $({\color{gray}0\%})$ 4_446 $({\color{gray}0\%})$ 3_847 $({\color{gray}0\%})$
Pop 150 front&back 92_095 $({\color{gray}0\%})$ 304_908 $({\color{gray}0\%})$ 124_581 $({\color{gray}0\%})$

Heap

pure/Queue pure/RealTimeQueue mutable Queue
Initialize with 2 elements 324 B $({\color{gray}0\%})$ 300 B $({\color{gray}0\%})$ 352 B $({\color{gray}0\%})$
Push 500 elements 8.08 KiB $({\color{gray}0\%})$ 8.17 KiB $({\color{gray}0\%})$ 19.8 KiB $({\color{gray}0\%})$
Pop front 2 elements 240 B $({\color{gray}0\%})$ 240 B $({\color{gray}0\%})$ 192 B $({\color{gray}0\%})$
Pop 150 front&back -4.42 KiB $({\color{gray}0\%})$ -492 B $({\color{gray}0\%})$ -11.45 KiB $({\color{gray}0\%})$

Garbage Collection

pure/Queue pure/RealTimeQueue mutable Queue
Initialize with 2 elements 508 B $({\color{gray}0\%})$ 444 B $({\color{gray}0\%})$ 456 B $({\color{gray}0\%})$
Push 500 elements 10.1 KiB $({\color{gray}0\%})$ 137.84 KiB $({\color{gray}0\%})$ 344 B $({\color{gray}0\%})$
Pop front 2 elements 12.19 KiB $({\color{gray}0\%})$ 528 B $({\color{gray}0\%})$ 424 B $({\color{gray}0\%})$
Pop 150 front&back 15.61 KiB $({\color{gray}0\%})$ 49.66 KiB $({\color{gray}0\%})$ 12.1 KiB $({\color{gray}0\%})$

Note: Renamed benchmarks cannot be compared. Refer to the current baseline for manual comparison.

@rvanasa rvanasa enabled auto-merge (squash) January 27, 2026 15:42
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