Types & objects

Extension Functions

Extension functions allow adding methods to existing types:

# Extension for int
ext(int a) max(int b) int {
    return if (a > b) then a else b
}

# Extension for str
ext(str a) insert(int index, str s) str {
    return a.sub(0, index).con(s).con(a.sub(index, a.len()))
}

# Usage
int maxValue = 5.max(10)  # 10
str result = "Hello".insert(5, " World")  # "Hello World"

No-Argument Extensions

An extension with no parameters is still called with (). Like every method and conversion, the parentheses are required — bare access is only for stored fields:

ext(bool b) label() str {
    return if b then "on" else "off"
}

ext(int n) double() int {
    return n * 2
}

# Usage — parentheses are required:
bool flag = true
str s = flag.label()  # "on"

int x = 5
int d = x.double()  # 10
# int bad = x.double;  # ERROR: 'double' is a function; call it with parentheses: double()

Pick names that don't collide with a built-in method: an extension shadows a built-in of the same name (e.g. an ext(bool b) str() would hide the built-in bool.str()), which is rarely what you want.

Extension for Classes

ext(Terminal t) printInt(int a) void {
    t.println(a.str())
}

Terminal term = new Terminal()
term.printInt(42)  # Will print "42"