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Specification 6.0 · Not released · Tested product 5.21.3

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    Library · Collections

    Map.length for K, V

    Inspect the declaration, parameters, and availability of this API.

    length: int
    Receiver
    Map<K, V>
    Minimum arity
    0
    Maximum arity
    0

    Declaration and parameters

    Link

    Availability

    Included by default: yes

    These types are provided by the language. No module import is required.

    The declarations below describe the standard operations on built-in values.

    Source evidence

    Receiver

    Map<K, V>

    Parameter constraints

    Additional contracts are Pending.

    Test whether a Bytes, Map, or Set value is empty by comparing its length property with zero. The comparison is true exactly when the collection has no bytes, entries, or elements.

    Bytes, Map, and Set do not expose an isEmpty member. Read the length property and use the ordinary equality operator.

    Related rule: Test collection emptiness with length

    Result

    Additional contracts are Pending.

    The declared result type is int.

    Effects

    Pending

    Failures

    Pending

    Result and effects

    Link

    Select this field from a value of its named type without call parentheses.

    Runtime behavior, boundary inputs, effects, and failures remain Pending until their source contracts and public CLI observations are reviewed.

    Related entries

    Link

    Collections

    Test collection emptiness with length

    Link
    Ruletopaz.stdlib.contract.collection-emptiness.rule

    Test collection emptiness with length

    Test whether a Bytes, Map, or Set value is empty by comparing its length property with zero. The comparison is true exactly when the collection has no bytes, entries, or elements.

    Bytes, Map, and Set do not expose an isEmpty member. Read the length property and use the ordinary equality operator.

    Why

    A collection already exposes its count through length. Comparing that value with zero expresses emptiness for every collection without another query name or a type-specific method.

    Examples Test empty and nonempty maps with lengthTest empty and nonempty sets with lengthTest empty and nonempty byte sequences with lengthReject Bytes.isEmptyReject Map.isEmptyReject Set.isEmpty

    Diagnostics TPZ5006

    Source evidence

    Test empty and nonempty maps with length

    Link

    run · running · Verification: not-run

    main.tpzTest empty and nonempty maps with lengthOpen in Playground
    1. import std.io
    3. let empty: Map<string, int> = map {}
    4. let filled = map { "one": 1 }
    5. io.writeLine("{empty.length == 0}:{filled.length == 0}")
    Expected outputexit 0
    true:false
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. true:false

    This exact example has not been executed.

    Source evidence

    Test empty and nonempty sets with length

    Link

    run · running · Verification: not-run

    main.tpzTest empty and nonempty sets with lengthOpen in Playground
    1. import std.io
    3. let empty: Set<int> = set {}
    4. let filled = set { 1 }
    5. io.writeLine("{empty.length == 0}:{filled.length == 0}")
    Expected outputexit 0
    true:false
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. true:false

    This exact example has not been executed.

    Source evidence

    Test empty and nonempty byte sequences with length

    Link

    run · running · Verification: not-run

    main.tpzTest empty and nonempty byte sequences with lengthOpen in Playground
    1. import std.bytes { Bytes }
    2. import std.test
    3. import std.io
    5. let empty = Bytes.empty()
    6. let filled = test.assertOk(Bytes.fromArray([1]))
    7. io.writeLine("{empty.length == 0}:{filled.length == 0}")
    Expected outputexit 0
    true:false
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    No stderr.

    Expected stdout
    1. true:false

    This exact example has not been executed.

    Source evidence

    Reject Bytes.isEmpty

    Link

    reject · checking · Verification: not-run

    main.tpzReject Bytes.isEmptyOpen in Playground
    1. import std.bytes { Bytes }
    2. function inspect(value: Bytes) -> () {
    3. let result = value.isEmpty()
    4. return ()
    5. }
    Expected outputNonzero exit
    No stdout.
    $ topaz check main.tpz --format json · target product 5.21.3
    Expected result

    Expected result

    Rejection during check. Nonzero exit.

    • TPZ5006 stdlib-removed-member at main.tpz:3:22

    No stdout.

    This exact example has not been executed.

    Source evidence

    Reject Map.isEmpty

    Link

    reject · checking · Verification: not-run

    main.tpzReject Map.isEmptyOpen in Playground
    1. function inspect(value: Map<string, int>) -> () {
    2. let result = value.isEmpty()
    3. return ()
    4. }
    Expected outputNonzero exit
    No stdout.
    $ topaz check main.tpz --format json · target product 5.21.3
    Expected result

    Expected result

    Rejection during check. Nonzero exit.

    • TPZ5006 stdlib-removed-member at main.tpz:2:22

    No stdout.

    This exact example has not been executed.

    Source evidence

    Reject Set.isEmpty

    Link

    reject · checking · Verification: not-run

    main.tpzReject Set.isEmptyOpen in Playground
    1. function inspect(value: Set<int>) -> () {
    2. let result = value.isEmpty()
    3. return ()
    4. }
    Expected outputNonzero exit
    No stdout.
    $ topaz check main.tpz --format json · target product 5.21.3
    Expected result

    Expected result

    Rejection during check. Nonzero exit.

    • TPZ5006 stdlib-removed-member at main.tpz:2:22

    No stdout.

    This exact example has not been executed.

    Source evidence

    Diagnostics

    Link

    Unknown member or field

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