### Interacting
#### Output
[ Entity standard-out Funcon print ] Entity _ -- standard-out!(_:values*) -> _
*/ Funcon print(_:values*) : =>null-type
/* `print(X*)` evaluates the arguments `X*` and emits the resulting sequence of
values on the standard-out channel. `print( )` has no effect.
*/
Ruleprint(V*:values*) -- standard-out!(V*) -> null-value
#### Input
[ Entity standard-in Funcon read ] Entity _ -- standard-in?(_:values*) -> _
/* This entity represents the sequence of values input by a particular
transition, where the empty sequence `( )` represents that no values are
input. The value `null-value` represents the end of the input.
Composition of transitions concatenates their input sequences, except that
when the first sequence ends with `null-value`, the second seqeunce has to be
just `null-value`.
*/ Funcon read : =>values
/* `read` inputs a single value from the standard-in channel, and returns it.
If the end of the input has been reached, `read` fails.
*/
Ruleread -- standard-in?(V:~null-type) -> V Rule read -- standard-in?(null-value) -> fail
/*This entity represents the sequence of values output by a particular transition, where the empty sequence `( )` represents the lack of output. Composition of transitions concatenates their output sequences.