Strings and slicing#

Both single and double quotes create strings. Boolean literals are true and false (lowercase). Strings are immutable values: these methods return results without changing the original binding.

Characters#

A character is one Unicode extended grapheme cluster: a visible character can contain multiple Unicode code points. Chinese 中, Japanese あ, Arabic عَ, é, 🇨🇳, 👍🏽, and 👨‍👩‍👧‍👦 each count as one.

Length, iteration, reversal, and slicing all use this unit. They do not normalize the text. Segmentation uses the Rust unicode-segmentation crate (Unicode extended grapheme cluster rules); its Unicode version follows the crate version.

Methods#

Call	Result
`text.len()`	Number of characters
`text.reverse()`	New string with characters in reverse order
`text.slice(start,end)`	New string selecting positions `[start,end)`
`text.lenslice(start,length)`	New string selecting `length` characters from `start`
`text.copy()`	The same immutable string value

len() and reverse() take no arguments. Use text.lenslice(index,1) to extract one character; string bracket indexing is not implemented.

Counting from the end#

Both slicing methods accept an optional third boolean argument. It defaults to false. Write reverse=true or pass true positionally. A boolean expression is also accepted. Named reverse= must follow exactly two positional arguments and must be last. No other named arguments are supported.

With reverse=true, position zero is the last character. Selection proceeds toward the beginning, but the result keeps the original text order.

Expression	Result
`"ABCDE".lenslice(0,3)`	`"ABC"`
`"ABCDE".lenslice(0,3,reverse=true)`	`"CDE"`
`"ABCDE".lenslice(1,3,reverse=true)`	`"BCD"`
`"ABCDE".slice(1,4,reverse=true)`	`"BCD"`
`"ABCDE".lenslice(0,3,reverse=true).reverse()`	`"EDC"`

For slice, the end remains exclusive in the chosen direction. For a string of length N, reverse slice(start,end) selects the forward interval [N-end,N-start). Reverse lenslice(start,length) selects [N-start-length,N-start).

Bounds and errors#

Positions and lengths must be integers. Fractional values, strings, and booleans raise TypeError; longint values are accepted when within range.
Negative positions/lengths, starts beyond the string length, reversed intervals (end < start), and ranges exceeding available characters raise OutOfBoundsError.
A zero-length slice returns "". Its start may equal the string length, in either direction. The empty string accepts lenslice(0,0) and slice(0,0).
Two or three arguments are required. The optional reverse value must be a boolean; invalid arity or flag type raises TypeError.

Slices never silently truncate. For example, "ABC".lenslice(0,4) raises OutOfBoundsError, and "ABC".lenslice(3,0,reverse=true) returns "".

Iteration#

mars

func m{
    for (ch, "中é👨‍👩‍👧‍👦"){
        out(ch);
        out(ch.len()); // Each prints 1.
    }
}

Only the string APIs listed here are supported language contracts. Calling any other method on a string raises TypeError.