Trait endbasic_core::syms::Command

pub trait Command {
    fn metadata(&self) -> &CallableMetadata;
    fn exec<'life0, 'life1, 'life2, 'async_trait>(
        &'life0 self, 
        args: &'life1 [(Option<Expr>, ArgSep)], 
        machine: &'life2 mut Machine
    ) -> Pin<Box<dyn Future<Output = CommandResult> + 'async_trait>>
    where
        'life0: 'async_trait,
        'life1: 'async_trait,
        'life2: 'async_trait,
        Self: 'async_trait;
}

A trait to define a command that is executed by a Machine.

The commands themselves are immutable but they can reference mutable state. Given that EndBASIC is not threaded, it is sufficient for those references to be behind a RefCell and/or an Rc.

Idiomatically, these objects need to provide a new() method that returns an Rc<Callable>, as that’s the type used throughout the execution engine.

Required methods

fn metadata(&self) -> &CallableMetadata

Returns the metadata for this command.

The return value takes the form of a reference to force the callable to store the metadata as a struct field so that calls to this function are guaranteed to be cheap.

fn exec<'life0, 'life1, 'life2, 'async_trait>(
    &'life0 self,
    args: &'life1 [(Option<Expr>, ArgSep)],
    machine: &'life2 mut Machine
) -> Pin<Box<dyn Future<Output = CommandResult> + 'async_trait>> where
    'life0: 'async_trait,
    'life1: 'async_trait,
    'life2: 'async_trait,
    Self: 'async_trait, 

Executes the command.

args contains the arguments as provided in the invocation of the command. Each entry in this array contains an optional expression (to support things like PRINT a, , b) and the separator that was used between that argument and the next. The last entry in args always has ArgSep::End as the separator.

machine provides mutable access to the current state of the machine invoking the command.

Commands cannot return any value except for errors.

Implementors