python coroutines and generators

3.26: adda/type/streams/python coroutines and generators:
. after seeing python's coroutines and generators,
I was noticing that its function's signatures weren't explicit;
the syntax for generating coroutine should be:
f(x.stream.t1).stream.t2 .
. this tells you that when you pass f a file, x, of type t1,
it keeps reading units until you close x,
and it expects to be assigned to a stream,
which it continues to write to until f's input is closed .
y,x: stream; y`= f(x);
-- this causes f to function its stream .
. readers wait if x`item = eof
until there's a value to read .