Struct Ctx 

pub struct Ctx<'a> {
    pub cfg: EvalCfg,
    pub out: &'a mut dyn FnMut(&str),
    pub env: &'a mut Env,
    pub device: Option<&'a Device>,
}

Execution context threaded through evaluation.

Fields

cfg: EvalCfg

out: &'a mut dyn FnMut(&str)

Sink for explicit output (echo, ⎕←). stdout by default per the sandbox contract; the host may redirect.

env: &'a mut Env

The names the program has bound so far.

device: Option<&'a Device>

Where the run was placed. None is the CPU, which is also what every path that cannot use a device does; only a fused node reads it.