map¶

Extra map methods on top of the built-in ones.

import "std/map";

A map holds key-value pairs. The core operations are built-in methods on a map value (m.len(), m.get(k), m.insert(k, v), m.remove(k), m.contains(k), m.keys(), m.values(); listed in built-in functions), and a map iterates its keys:

fn main() {
    let m = {"a": 1, "b": 2};
    for k in m {
        print(k + "=" + str(m.get(k)));
    }
}

This module adds conveniences in an impl map block (see methods); the import brings them in. Map literals are described in collections.

The methods are polymorphic through compile-time monomorphisation: one definition specialises to whatever key and value types the call site uses. The module is pure candela, so it compiles into a .cdlb artifact and runs under candela-vm with no dynamic library.

is_empty¶

m.is_empty()

• Returns: a bool, true when the map has no entries.

get_or¶

m.get_or(k, default)

• k: a key of the map's key type.
• default: the value to return when the key is absent; the same type as the map's values.
• Returns: the value stored under k, or default.
• Raises: nothing.

import "std/map";

fn main() {
    let counts = {"a": 1};
    print(counts.get_or("a", 0));
    print(counts.get_or("z", 0));
}

A map keeps its entries in the order they went in, and every walk over one follows that order. The rules for where an entry lands are in built-in functions.