rs-0.17.0 — Errors that say where, f-strings, tests, and big numbers#

The biggest release yet: runtime errors now show the line and the calls that led there, strings can hold values with f"...", programs can be tested with marslang test, integers can be any size, and eight new standard packages reach the network, the terminal, and the rest of the world.

Errors say where#

text

error: RangeError: random.int_between needs low <= high, got 6 and 1
    at roll (dice.mars:4)
    at Game.play (game.mars:7)
    at m (game.mars:14)

Every uncaught error prints its line and the calls that led there, innermost first, as file:line, which editors open with a click. Calls inside the standard library are left out, and recursion collapses to one line with its count. Compile errors such as unknown name 'nope' now say their line too, and the VS Code extension underlines the exact name.

f-strings#

mars

func m{
    name = "Ada";
    age = 36;
    out(f"{name} is {age}, and {age + 1} next year");   // Ada is 36, and 37 next year
}

Any expression goes between the braces; {{ and }} are braces. A string inside the braces uses the other quote: f"{scores.get('ada')}". See f-strings.

Tests: std.testing and marslang test#

marslang test runs every function named test_... in every *_test.mars file, each on its own: a failure shows the line of the assertion and the next test runs, and the command ends with status 1 when anything failed. std.testing has equal (which compares containers by contents), not_equal, is_true, is_false, close, raises, and fail.

bigint: integers of any size#

bigint(2) ** 200, bigint("123456789012345678901234567890"), and literals beyond longint are a new kind, bigint, with every operator. Ints and longints mix with it; floats need an explicit conversion; equal numbers of every kind are the same map key. json.parse reads huge integers as bigints. std.bigint adds gcd, lcm, factorial, integer square root, floor division, and bases 2 to 36.

New packages#

Package	For
std.http	Fetching pages, JSON APIs, and downloads over HTTPS, through proxies from the environment
std.format	`fixed(3.14159, 2)`, `number(1234.5, 2)` is `"1,234.50"`, percentages, and tables that line up even with Chinese and emoji
std.terminal	Colours and styles, progress bars, and the terminal's size, respecting `NO_COLOR`
std.log	`log.info(...)` with levels and timestamps, to standard error or a file
std.hash	SHA-256, SHA-512, SHA-1, MD5, CRC-32 of text and files, and HMAC
std.encoding	base64, hex, URL encoding, query strings, and bytes
std.testing	Assertions for `marslang test`
std.bigint	Integer arithmetic on bigints

Smaller changes#

A statement can go on over several lines inside ( ) or [ ], so long calls and arrays can be laid out; a bracket left open says where.
The installers find the latest release without GitHub's API, whose limit of 60 lookups an hour per address made installs fail on shared networks.
Release binaries are stripped: about 30% smaller, even with HTTPS added.
types.family_name(RangeError) names a family itself.

Validation#

cargo test passes 300 tests on Linux and 298 on Windows, including the new packages' own test files; HTTP is tested against a local server. Every push runs them on Windows, macOS, and Linux on x86_64 and ARM64, and runs the static Linux binary inside Alpine, Debian 11, Ubuntu 20.04, Rocky Linux 8, and Amazon Linux 2.