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Standard Library Naming

The standard library should name features in a consistent and clear way. Ideally, the expectations on the naming from developers used to other languages should be met as much as possible.


The standard library should provide immutable and mutable features, while the default should be immutable.

Fuzion should have syntactic sugar for the creation of arrays, lists and maps with pre-defined values. These values could be compile-time constants or run-time variables.

Some languages, such as Python and Go have on single function that can be used on most basic types, such as strings, arrays, maps/dictionaries, etc.:

in Python: len("hello world")

in Go:

x := map[String]int {"one": 1, "two": 2}

In Python, len() even works with higher level data types such as collections.deque. Similarly, in Go the convention seems to be to define a Len function for higher level data types such as List and Ring in the container part of the standard library.

In D, strings are a special case of arrays, and the number of elements in an array is returned by the .length property. Dynamic arrays and container types in D additionally have a .capacity property which gives the maximum number of elements that can be stored in the container.

Some languages use things such as sizeof to measure the amount of memory used by an array in bytes or the amount of memory needed by the pointer pointing to the collection. The latter seems rather unnecessary.

In other languages, naming of the function used to measure the cardinality of some object differs depending on the type of this object.


in Java: String.length()

in Kotlin: String.length

in Rust:

let a = String::from("foo");
assert_eq!(a.len(), 3);


in Java: array.length

in Kotlin: Array.size

in Rust: arr.len()

in F#: let arr = [| 1; 2; 3; 4; 5; 6 |]


in Java: ArrayList.size();

in Kotlin: ArrayList.size

Maps, Sets

in Java: Set.size()

in Kotlin: HashMap.size

in Rust:

// for number of elements
// for maximum number of elements that can be contained without reallocation


Some languages, such as Kotlin, offer a separate function count. Without arguments, this does the same as length or size; however it can be given a predicate, i.e. a function from a character, or an element of an array, or an entry of a map to a boolean value. In this case the number of elements for which the predicate returns true is counted.