Make select.case a little more readable

[wangkuiyi]

It looks to me that

sel = fluid.select()
with sel.read_case(ch, x):
  do_something_with(x)

is a little more readable than

sel = fluid.select()
with sel.case(ch, X, 'r'):
  do_something_with(x)

What do you think?

[helinwang]

What is your opinion on:

sel = fluid.select()
with sel.case(ch.read(), x):
  do_something_with(x)

[kavyasrinet]

I agree with both proposals.
For the first proposal, we will have to implement sel.read_case(ch, x) and sel.write_case(ch, x) methods as a part of select.
For the second proposal, we can have more consistency and can reuse concepts from channel implementation. Since in the PR: #8164 , the proposal is to make send and recv as functions of fluid instead of channel. So one proposal is:

sel = fluid.select()
with sel.case(fluid.recv(ch), x):
  do_something_with(x)

[abhinavarora]

I agree with @wangkuiyi first proposal of using

sel = fluid.select()
with sel.read_case(ch, x):
  do_something_with(x)

@helinwang , I like your suggestion too. I am just a little skeptic that since we will have to implement it for both the cases, i.e. the standalone channel and select, we might run into complications. I think we can start off with Yi's first suggestion and then later see if we can support your design. What do you think?