E041: I don't know a function by that name

You called a function – something with parentheses after it, like do_something() – and Turf couldn’t find any function with that exact name anywhere it looked: not in this file, not among the built-ins, not through anything you’ve imported.

fn greet(name: string): void {    printline("Hello, " + name);}greet("world");   // works -- "greet" is declared right above

Usually this is just a small typo in the function’s name:

grete("world");   // typo! should be "greet"

Just like with variable names, Turf will often notice a close match nearby and suggest it for you, so check the error message for a suggestion before anything else.

If it’s not a typo, the function might genuinely not exist yet in your code (you can write it yourself with fn), or it might live in a standard-library module you haven’t imported. Things like strings::length(...) or mem::malloc(...) need their module imported first with import strings; or import mem; before Turf can see them. Once the name matches something real and reachable, you’re good to go.

One more cause, specific to types: Turf has no constructor-call syntax, so Node(5) for a struct named Node is an unknown function too – the error’s hint says so when that is what happened. Build the value with Node::new(5) (if Node declares a .new method) or Node::default(), and for an enum or error type name one of its variants (Color::Red).

Run turf --explain E041 in a terminal to read this again.