Build text with recoverable allocation

Concatenating strings can need new storage, so + returns Result[str, AllocError]. Handle that result before using the new text:

def main() -> Result[(), AllocError | IoError]:
    message = ('Hello, ' + "Plenty!")?
    print(message)?
    print(contains(message, "Plenty"))?
    Ok(())

Hello, Plenty!
True

Building the string can fail with AllocError; printing can fail with IoError. The AllocError | IoError sum lets this function propagate either cause while keeping its original type and details.

Use str.from(value) to convert a scalar to text, or str.repr(value) for a representation such as quoted text or a displayed result wrapper. Both return allocation results; see the text conversion lessons.

A helper can combine construction and printing behind one result:

def greet(name: str) -> Result[(), AllocError | IoError]:
    print(("Hello, " + name)?)?
    Ok(())

def greet_if(enabled: bool, name: str) -> Result[(), AllocError | IoError]:
    if not enabled:
        return Ok(())
    greet(name)

def main() -> Result[(), AllocError | IoError]:
    greet_if(False, "Ada")?
    greet_if(True, "Ada")?
    Ok(())

Hello, Ada

String-building operations return allocation results even when a particular short string fits inline. A slice such as name[1:]? is another: it copies part of the text.