Function interp_debug 

fn interp_debug(
    _args: &[RValue],
    _named: &[(String, RValue)],
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Set a function for debug-mode single-stepping (stub).

miniR does not support interactive debugging. Prints a message.

@param fun function to debug @return invisible NULL