Strings

The string type is a fixed length value defined with str<N>.

You can use strings in assert() functions or print them with std::println(). See more about Logging.

use dep::std;

fn main(message : pub str<11>, hex_as_string : str<4>) {
    std::println(message);
    assert(message == "hello world");
    assert(hex_as_string == "0x41");
}

You can convert a str<N> to a byte array by calling as_bytes() or a vector by calling as_bytes_vec().

fn main() {
    let message = "hello world";
    let message_bytes = message.as_bytes();
    let mut message_vec = message.as_bytes_vec();
    assert(message_bytes.len() == 11);
    assert(message_bytes[0] == 104);
    assert(message_bytes[0] == message_vec.get(0));
}

Escape Characters

You can use escape characters for your strings:

Escape Sequence	Description
\r	Carriage Return
\n	Newline
\t	Tab
\0	Null Character
\"	Double Quote
\\	Backslash

Example:

let s = "Hello \"world"; // prints "Hello "world"
let s = "hey \tyou"; // prints "hey   you"

Formatted Strings

You can prepend a string with the singular f token to create a formatted string. This is useful when logging, as it allows injection of local variables:

let var = 15;
std::println(f"var {var}") // prints "var 0x0F"

let var = -1 as u8;
std::println(f"var {var}") // prints "var 255"

let var : i8 = -1;
std::println(f"var {var}") // prints "var -1"

// prints "Hello
//world"
std::println(f"Hello
world");

std::println(f"hey \tyou"); // prints "hey \tyou"

A type can be specified to print numbers either as hex via Field, unsigned via u* types and signed via i* types.

Note that escaped characters in formatted strings fmtstr will be outputted as defined, i.e. "\n" will be printed \n, not as a new line. You can add a newline or other whitespace by creating a multiline string as in the example above.