pub type OutputCallback<const N: usize> = fn(&Lisp<N>, ArenaIndex);Expand description
Function pointer type for output callbacks
This function is called by display and newline builtins during evaluation,
including during macro expansion. The function receives the evaluator’s lisp
context and the value to display.
Special handling for newline: The newline builtin passes nil as the
value parameter. Callbacks should check val.is_nil() to distinguish between
newline requests and actual display values.