Strings: Interpolation

● Beginner2 min

Write any expression in braces inside a string, and its value is put in its place.

fn main() {
    const name = "asha"
    const age = 31
    print("{name} turns {age} this year")
}

kavach run insert.kav

asha turns 31 this year

The braces can hold a calculation too. To write a brace itself, put a backslash before it:

fn main() {
    const items = 3
    const price = 40
    print("{items} items cost {items * price}")
    print("a literal brace: \{items}")
}

kavach run interp.kav

3 items cost 120a literal brace: {items}

In text on one line, a { must close on that line. One left open is an error at the brace, with the fix:

fn main() {
    const open = "{"
    print("a brace: {open}")
}

kavach run brace-open.kav

error: this `{` is never closed: write `\{` for a brace in text (spec 1.7)

A {…} that holds only text gives a warning, because it is almost always a brace that needed \{. Here the second line is one string, with the text or t == inside its braces, not two comparisons:

fn is_brace(t: String) -> Bool {
    t == "{" or t == "}"
}

fn main() {
    print(is_brace("\{"))
    print(is_brace(" or t == "))
}

kavach run brace-text.kav

warning: this `{…}` holds only text, so the string goes on past it: write `\{` for a brace, or the text itself (spec 1.7)falsetrue

tested the warning, tested