Still, I believe that if you really care about making the structure of
the code clear, then you would be well advised to (a) avoid inverting
the sense of boolean tests, and (b) avoid relying on the fact that one
arm of a conditional has a control transfer so that you can “get away
with” saving a level of horizontal indentation.
I think the clarity knife sometimes cuts in this direction, but
sometimes in the other direction.
If I have:
if (x instanceof P(var y)) {
// more than a page of code
}
else
throw new FooException();
vs
if (!(x instanceof P(var y)))
throw new FooException();
// the same page of code
In the latter case, i've checked all my preconditions up front, so it's
more obviously fail-fast. Maintainers are less likely to forget the
condition they just tested a page ago, and readers are more able to
build a mental model of the invariants of the happy path for this
method. So I think it's not always about "saving indentation"; in this
case it's "get the precondition checks out of the way, and set me up to
do the work without further interruption."
