Runtime

Panics

A panic is a hard, unrecoverable runtime error. It prints a message and exits the process with a non-zero status. Panics cannot be caught.

Panics are triggered by:

• .yolo() on None or a Result::Err
• Out-of-bounds array access
• Integer division by zero
• assert(false) or assert_msg(false, msg)

Built-in Functions

These are available in every module without any import declaration (provided by std::core auto-import):

Name	Signature	Description
print	<T>(v: T)	Print to stdout, no newline
println	<T>(v: T)	Print to stdout with newline
string_len	(s: String) -> Int	Number of characters in a string
string_concat	(a: String, b: String) -> String	Concatenate two strings
array_push	(arr: T[], value: T)	Append a value (mutates the array)
array_len	(arr: T[]) -> Int	Number of elements in an array
clock	() -> Int	Unix timestamp in milliseconds
assert	(cond: Bool)	Panic with "assertion failed" if cond is false
assert_msg	(cond: Bool, msg: String)	Panic with msg if cond is false
dbg	<T>(v: T) -> T	Print [dbg] <value> to stderr and return the value unchanged

Built-in Aspects

The following aspects are pre-implemented for built-in types:

Display

aspect Display {
    fun to_string(self) -> String;
}

Int, Float, Bool, and String implement Display. .to_string() returns the canonical string representation. print and println accept any Display type.

Iterable<T>

aspect Iterable<T> {
    fun next(mut self) -> Perhaps<T>;
}

T[] (array) and Range (from .. / ..=) implement Iterable<T>. User-defined types may implement it to be usable in for-in.

From<S>

aspect From<S> {
    fun from(value: S) -> Self;
}

Int implements From<Float> (truncating cast) and Float implements From<Int>. The as operator desugars to T::from(value). User-defined types may implement From<S> to enable as casts and ? error coercion.

String Methods

Method	Signature	Description
.len()	() -> Int	Number of characters in the string
.to_string()	() -> String	Returns the string itself