Add reduce function to arrays #4290

devin-ai-integration · 2025-10-14T19:28:00Z

Description

Adds a reduce function to arrays in Cadence with the signature:

fun reduce<U>(initial: U, _ f: fun (U, T): U): U

The implementation follows the same three-layer pattern as the existing map function:

sema/type.go: Type system definition with generic type parameter U for the accumulator type, allowing it to differ from the array element type T
interpreter/value_array.go: Runtime execution that iterates through array elements and applies the reducer function
bbq/vm/value_array.go: Bytecode registration for both variable-sized and constant-sized arrays

Changes

Type System

Added ArrayReduceFunctionType with generic type parameter U
Registered reduce function with resource array rejection (consistent with map)

Interpreter

Implemented ArrayValue.Reduce method that iterates and accumulates values
Added NativeArrayReduceFunction wrapper
Registered in GetMethod for array values

Tests

Moved TestInterpretArrayReduce from misc_test.go to array_test.go (per review feedback)
Added sema tests for:
- Basic reduce operations (sum, product)
- Fixed-size arrays
- Struct arrays with value-type elements
- Invalid arguments and type mismatches
- Resource arrays (correctly rejected)
Added interpreter tests for:
- Empty arrays (returns initial value)
- Type conversion (Int array → String accumulator)
- Mutation during iteration (correctly raises ContainerMutatedDuringIterationError)

Critical Review Areas

Generic type parameter handling: Verify ArrayReduceFunctionType correctly handles the case where accumulator type U differs from element type T
Struct array test: The test testStructArrayReduce operates on an unauthorized reference &[S] and mutates struct fields inside the reducer. This works because struct elements are passed by value (copies), not by reference. Verify this is the intended test case - it demonstrates that mutations happen on copies when using unauthorized references.
Resource array rejection: Confirm that rejecting reduce on resource arrays matches the intended behavior and is consistent with map

Link to Devin run: https://app.devin.ai/sessions/f6bc7843ea324388964f82a1cdc1b1b1
Requested by: [email protected]

Targeted PR against master branch
Linked to Github issue with discussion and accepted design OR link to spec that describes this work
Code follows the standards mentioned here
Updated relevant documentation
Re-reviewed Files changed in the Github PR explorer
Added appropriate labels

Implement array reduce function with signature: fun reduce<U>(initial: U, _ f: fun (U, T): U): U Changes: - sema: Define ArrayReduceFunctionType and register in getArrayMembers - interpreter: Implement ArrayValue.Reduce and NativeArrayReduceFunction - vm: Register reduce function for both variable and constant-sized arrays - tests: Add tests for reduce in arrays_dictionaries_test.go and misc_test.go

devin-ai-integration · 2025-10-14T19:28:31Z

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github-actions · 2025-10-14T19:34:41Z

Benchstat comparison

Base branch: onflow:master
Base commit: 3ec0c24

Results

	old.txt	new.txt
	time/op		delta
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4	392µs ± 0%	392µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ContractImport-4	215µs ± 0%	222µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ExportType/composite_type-4	265ns ± 0%	272ns ± 0%	~	(p=1.000 n=1+1)
ExportType/simple_type-4	77.8ns ± 0%	77.8ns ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
FTTransfer-4	122µs ± 0%	122µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-4	19.9µs ± 0%	20.5µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ImperativeFib-4	13.8µs ± 0%	14.2µs ± 0%	~	(p=1.000 n=1+1)
ImperativeFibNewCompilerNewVM-4	35.2µs ± 0%	35.5µs ± 0%	~	(p=1.000 n=1+1)
ImperativeFibNewVM-4	16.1µs ± 0%	16.7µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
InterpretRecursionFib-4	2.09ms ± 0%	2.22ms ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
InterpreterFTTransfer-4	109µs ± 0%	111µs ± 0%	~	(p=1.000 n=1+1)
InterpreterImperativeFib-4	20.8µs ± 0%	20.6µs ± 0%	~	(p=1.000 n=1+1)
InterpreterNewStruct-4	60.3µs ± 0%	61.5µs ± 0%	~	(p=1.000 n=1+1)
MethodCall/concrete_type_method_call-4	45.6µs ± 0%	45.6µs ± 0%	~	(all equal)
MethodCall/interface_method_call-4	67.5µs ± 0%	67.9µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
NewInterpreter/new_interpreter-4	1.03µs ± 0%	1.04µs ± 0%	~	(p=1.000 n=1+1)
NewInterpreter/new_sub-interpreter-4	348ns ± 0%	334ns ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
NewResource-4	85.9µs ± 0%	86.8µs ± 0%	~	(p=1.000 n=1+1)
NewStruct-4	32.6µs ± 0%	34.1µs ± 0%	~	(p=1.000 n=1+1)
NewStructRaw-4	3.73µs ± 0%	3.69µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/sema goos:linux goarch:amd64
QualifiedIdentifierCreation/One_level-4	2.49ns ± 0%	2.19ns ± 0%	~	(p=1.000 n=1+1)
QualifiedIdentifierCreation/Three_levels-4	85.1ns ± 0%	85.3ns ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
RecursionFib-4	782µs ± 0%	808µs ± 0%	~	(p=1.000 n=1+1)
RuntimeFungibleTokenTransfer-4	727µs ± 0%	722µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4	578µs ± 0%	574µs ± 0%	~	(p=1.000 n=1+1)
RuntimeFungibleTokenTransferVM-4	645µs ± 0%	625µs ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceDictionaryValues-4	2.63ms ± 0%	2.58ms ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceTracking-4	11.9ms ± 0%	11.9ms ± 0%	~	(p=1.000 n=1+1)
RuntimeScriptNoop-4	15.2µs ± 0%	14.4µs ± 0%	~	(p=1.000 n=1+1)
RuntimeVMInvokeContractImperativeFib-4	28.7µs ± 0%	28.5µs ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/sema goos:linux goarch:amd64
SuperTypeInference/arrays-4	231ns ± 0%	228ns ± 0%	~	(p=1.000 n=1+1)
SuperTypeInference/composites-4	90.8ns ± 0%	91.8ns ± 0%	~	(p=1.000 n=1+1)
SuperTypeInference/integers-4	308ns ± 0%	304ns ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-4	66.2ns ± 0%	71.8ns ± 0%	~	(p=1.000 n=1+1)

	alloc/op		delta
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4	152kB ± 0%	152kB ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ContractImport-4	73.8kB ± 0%	74.1kB ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ExportType/composite_type-4	120B ± 0%	120B ± 0%	~	(all equal)
ExportType/simple_type-4	0.00B	0.00B	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
FTTransfer-4	37.8kB ± 0%	37.8kB ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-4	8.30kB ± 0%	8.30kB ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ImperativeFib-4	1.94kB ± 0%	1.94kB ± 0%	~	(all equal)
ImperativeFibNewCompilerNewVM-4	21.8kB ± 0%	21.8kB ± 0%	~	(all equal)
ImperativeFibNewVM-4	4.66kB ± 0%	4.66kB ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
InterpretRecursionFib-4	1.19MB ± 0%	1.19MB ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
InterpreterFTTransfer-4	37.6kB ± 0%	37.6kB ± 0%	~	(p=1.000 n=1+1)
InterpreterImperativeFib-4	8.29kB ± 0%	8.29kB ± 0%	~	(all equal)
InterpreterNewStruct-4	24.4kB ± 0%	24.4kB ± 0%	~	(p=1.000 n=1+1)
MethodCall/concrete_type_method_call-4	6.94kB ± 0%	6.94kB ± 0%	~	(p=1.000 n=1+1)
MethodCall/interface_method_call-4	14.5kB ± 0%	14.5kB ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
NewInterpreter/new_interpreter-4	976B ± 0%	976B ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-4	232B ± 0%	232B ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
NewResource-4	40.4kB ± 0%	40.4kB ± 0%	~	(p=1.000 n=1+1)
NewStruct-4	10.3kB ± 0%	10.4kB ± 0%	~	(p=1.000 n=1+1)
NewStructRaw-4	2.57kB ± 0%	2.61kB ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/sema goos:linux goarch:amd64
QualifiedIdentifierCreation/One_level-4	0.00B	0.00B	~	(all equal)
QualifiedIdentifierCreation/Three_levels-4	64.0B ± 0%	64.0B ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
RecursionFib-4	88.1kB ± 0%	88.1kB ± 0%	~	(p=1.000 n=1+1)
RuntimeFungibleTokenTransfer-4	232kB ± 0%	232kB ± 0%	~	(p=1.000 n=1+1)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4	156kB ± 0%	155kB ± 0%	~	(p=1.000 n=1+1)
RuntimeFungibleTokenTransferVM-4	174kB ± 0%	173kB ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceDictionaryValues-4	1.76MB ± 0%	1.76MB ± 0%	~	(p=1.000 n=1+1)
RuntimeResourceTracking-4	9.26MB ± 0%	9.26MB ± 0%	~	(p=1.000 n=1+1)
RuntimeScriptNoop-4	7.99kB ± 0%	7.98kB ± 0%	~	(p=1.000 n=1+1)
RuntimeVMInvokeContractImperativeFib-4	10.3kB ± 0%	10.3kB ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/sema goos:linux goarch:amd64
SuperTypeInference/arrays-4	96.0B ± 0%	96.0B ± 0%	~	(all equal)
SuperTypeInference/composites-4	0.00B	0.00B	~	(all equal)
SuperTypeInference/integers-4	0.00B	0.00B	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-4	48.0B ± 0%	48.0B ± 0%	~	(all equal)

	allocs/op		delta
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ContractFunctionInvocation-4	2.47k ± 0%	2.47k ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ContractImport-4	931 ± 0%	931 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
ExportType/composite_type-4	3.00 ± 0%	3.00 ± 0%	~	(all equal)
ExportType/simple_type-4	0.00	0.00	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
FTTransfer-4	965 ± 0%	965 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ImperativeFib-4	176 ± 0%	176 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
ImperativeFib-4	49.0 ± 0%	49.0 ± 0%	~	(all equal)
ImperativeFibNewCompilerNewVM-4	210 ± 0%	210 ± 0%	~	(all equal)
ImperativeFibNewVM-4	86.0 ± 0%	86.0 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
InterpretRecursionFib-4	17.7k ± 0%	17.7k ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
InterpreterFTTransfer-4	788 ± 0%	788 ± 0%	~	(all equal)
InterpreterImperativeFib-4	175 ± 0%	175 ± 0%	~	(all equal)
InterpreterNewStruct-4	418 ± 0%	418 ± 0%	~	(all equal)
MethodCall/concrete_type_method_call-4	135 ± 0%	135 ± 0%	~	(all equal)
MethodCall/interface_method_call-4	285 ± 0%	285 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
NewInterpreter/new_interpreter-4	15.0 ± 0%	15.0 ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-4	4.00 ± 0%	4.00 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
NewResource-4	735 ± 0%	735 ± 0%	~	(all equal)
NewStruct-4	219 ± 0%	219 ± 0%	~	(all equal)
NewStructRaw-4	38.0 ± 0%	38.0 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/sema goos:linux goarch:amd64
QualifiedIdentifierCreation/One_level-4	0.00	0.00	~	(all equal)
QualifiedIdentifierCreation/Three_levels-4	2.00 ± 0%	2.00 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/bbq/vm/test goos:linux goarch:amd64
RecursionFib-4	3.65k ± 0%	3.65k ± 0%	~	(all equal)
RuntimeFungibleTokenTransfer-4	3.94k ± 0%	3.94k ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/runtime goos:linux goarch:amd64
RuntimeFungibleTokenTransferInterpreter-4	2.93k ± 0%	2.93k ± 0%	~	(all equal)
RuntimeFungibleTokenTransferVM-4	3.06k ± 0%	3.06k ± 0%	~	(all equal)
RuntimeResourceDictionaryValues-4	36.7k ± 0%	36.7k ± 0%	~	(all equal)
RuntimeResourceTracking-4	159k ± 0%	159k ± 0%	~	(p=1.000 n=1+1)
RuntimeScriptNoop-4	113 ± 0%	113 ± 0%	~	(all equal)
RuntimeVMInvokeContractImperativeFib-4	213 ± 0%	213 ± 0%	~	(all equal)
pkg:github.com/onflow/cadence/sema goos:linux goarch:amd64
SuperTypeInference/arrays-4	3.00 ± 0%	3.00 ± 0%	~	(all equal)
SuperTypeInference/composites-4	0.00	0.00	~	(all equal)
SuperTypeInference/integers-4	0.00	0.00	~	(all equal)
pkg:github.com/onflow/cadence/interpreter goos:linux goarch:amd64
ValueIsSubtypeOfSemaType-4	1.00 ± 0%	1.00 ± 0%	~	(all equal)

sema/type.go

Per review comment: add function signature comments similar to ArrayMapFunctionType

devin-ai-integration · 2025-10-15T03:16:32Z

Added comments in commit 86d3e8e. The function now includes:

Signature description: // fun reduce<U>(initial: U, _ f: fun (U, T): U): U
Type documentation: // reducerFuncType: (U, T) -> U

Similar to how ArrayMapFunctionType is documented.

interpreter/value_array.go

Per review comment: inline the argumentTypes slice directly in the invokeFunctionValue call

devin-ai-integration · 2025-10-15T03:17:26Z

Done in commit a8942f8. Inlined argumentTypes directly in the invokeFunctionValue call.

sema/type.go

function type is the same for variable-sized and constant-sized array types

Per review comment: Keep only the function signature comment

…git-manager.devin.ai/proxy/github.com/onflow/cadence into devin/1760470003-add-array-reduce-function

interpreter/value_array.go

…git-manager.devin.ai/proxy/github.com/onflow/cadence into devin/1760470003-add-array-reduce-function

sema/arrays_dictionaries_test.go

…based inner array mutation; update expectations

sema/arrays_dictionaries_test.go

interpreter/misc_test.go

…eference test

devin-ai-integration bot requested review from RZhang05, SupunS and turbolent as code owners October 14, 2025 19:28

turbolent self-assigned this Oct 14, 2025

turbolent added the Feature label Oct 14, 2025

turbolent reviewed Oct 15, 2025

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sema/type.go Show resolved Hide resolved

Add comments to ArrayReduceFunctionType

86d3e8e

Per review comment: add function signature comments similar to ArrayMapFunctionType

turbolent reviewed Oct 15, 2025

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interpreter/value_array.go Outdated Show resolved Hide resolved

Inline argumentTypes in Reduce method

a8942f8

Per review comment: inline the argumentTypes slice directly in the invokeFunctionValue call

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turbolent and others added 3 commits October 14, 2025 20:18

remove unnecessary line

4f3c2d7

function type is the same for variable-sized and constant-sized array types

Remove unnecessary 'For [T]' comment line

d96679b

Per review comment: Keep only the function signature comment

Merge branch 'devin/1760470003-add-array-reduce-function' of https://…

cf2415e

…git-manager.devin.ai/proxy/github.com/onflow/cadence into devin/1760470003-add-array-reduce-function

turbolent reviewed Oct 15, 2025

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interpreter/value_array.go Outdated Show resolved Hide resolved

Update interpreter/value_array.go

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turbolent approved these changes Oct 15, 2025

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Merge branch 'devin/1760470003-add-array-reduce-function' of https://…

eda0b30

…git-manager.devin.ai/proxy/github.com/onflow/cadence into devin/1760470003-add-array-reduce-function

turbolent mentioned this pull request Oct 15, 2025

Add reduce function to arrays #4296

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RZhang05 reviewed Oct 15, 2025

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sema/arrays_dictionaries_test.go Show resolved Hide resolved

sema: add reduce invalid-args tests for invalid initial type and ref-…

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…based inner array mutation; update expectations

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interpreter/misc_test.go Outdated Show resolved Hide resolved

Add test for mutation during reduce

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interpreter/misc_test.go Outdated Show resolved Hide resolved

Move TestInterpretArrayReduce to array_test.go and add struct-array r…

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…eference test

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