rs-0.12.0 — Functions as values, string methods, and std.cli#

Functions can now be written inline and passed around, strings gain the methods text processing needs, and programs can read their command line. The syntax is written down in full in the new grammar page.

Anonymous functions and closures#

func(type name) => expression makes a function without a name, and a func declared inside a block is a local function. Both close over the variables around them by reference, so a counter keeps its count:

mars

func apply(Function f, int x) => f(x);

func counter(){
    count = 0;
    func next(){
        count = count + 1;
        ret count;
    }
    ret next;
}

func m{
    double = func(int x) => x * 2;
    out(apply(double, 21));   // 42
    tick = counter();
    tick(); tick();
    out(tick());              // 3
}

Function and Family are parameter types for code that takes a function or a family as an argument; they are not allowed on variables. Inside a method, a closure keeps me and the family's private access. Closures made in a loop share the loop variable, as in Python; see functions as values.

Strings#

s[i] and a[i] read one character or element, counting whole characters, and strings gain iget(i) to match arrays. Indexing is read-only: change an array element with modify(i, value).

Method	Result
`split()`, `split(sep)`	Pieces around whitespace, or around `sep`
`lines()`	The lines, without their line endings
`strip()`, `lstrip()`, `rstrip()`	Without surrounding whitespace, or the given characters
`upper()`, `lower()`	Changed case
`replace(old, new)`	Every `old` replaced by `new`
`find(x)`, `rfind(x)`	The first or last position of `x`, or `-1`
`contains(x)`, `starts_with(x)`, `ends_with(x)`	Booleans

mars

out("  name, age ,city  ".strip().split(","));   // ["name", " age ", "city"]
out("héllo👋"[5]);                               // 👋

std.cli#

Words after the program's file are now the program's arguments: marslang greet.mars --name Ada --loud. std.cli reads them with args(), parses --flags, --options, and positionals with cli.parser, prints a generated --help, and stops with an exit status through cli.exit(code). An exit passes every handle, but then blocks still run. See std.cli.

Integer literals beyond 32 bits#

A whole-number literal that does not fit in 32 bits is now a longint, so 3000000000 + 1 is 3000000001. It used to be an int that printed but raised int overflow in any arithmetic. Passing one to an int parameter still raises int overflow.

Fixes#

marslang lex understands triple-quoted strings and escaped quotes.
The README no longer describes the package directory as planned.
Every push is now tested on Linux and Windows.

Validation#

cargo test passes 126 tests (13 unit, 112 execution, 1 memory) on Windows Rust and on WSL-native Rust. The memory test now covers cycles through closures.