|
|
|
|
# If A Function Description Includes An "And", It's Wrong
|
|
|
|
|
|
|
|
|
|
Functions should do one thing and one thing only. I clear indication that
|
|
|
|
|
you're breaking this principle is the need to add an "and" in its
|
|
|
|
|
documentation.
|
|
|
|
|
|
|
|
|
|
This is kind like "sometimes rule", but most of the time, when you feel you
|
|
|
|
|
need to add an "and" to the function documentation (its
|
|
|
|
|
[contract](./document-is-contract.md)), then you're telling
|
|
|
|
|
that that function is doing two (or more) things.
|
|
|
|
|
|
|
|
|
|
One of guiding principles of good code is the [Single responsibility
|
|
|
|
|
principle](https://en.wikipedia.org/wiki/Single_responsibility_principle), in
|
|
|
|
|
which each module/class/function should do one thing and one thing only. And,
|
|
|
|
|
again, if you're saying that a function is doing "this" _and_ "that", you can
|
|
|
|
|
be sure it's not doing just _one_ thing.
|
|
|
|
|
|
|
|
|
|
Ok, but what now? Well, you have two functions, with two distinct contracts.
|
|
|
|
|
Ok, but you _had_ those two being called, what happens now? Well, where you
|
|
|
|
|
called one, you now will need to call two. If your preferred language have
|
|
|
|
|
support for function composition, you can use that to group both functions
|
|
|
|
|
again. This is the kind of stuff that you'll get when you [learn to use
|
|
|
|
|
functional programming](../before/functional-programming.md).
|
