2016-12-29
One reason why Go's increment and decrement statements are good to have
Go is generally a minimal language as far
as both language keywords and features go. It's not quite down to
Scheme level minimalism, it's far
more pragmatic than that, but it does try to be small. In among
this smallness, one thing may stand out; I'm thinking of the increment
and decrement statements,
'i++' and 'j--'.
There's strictly speaking no need for these to exist. Since Go makes
them statements instead of operators, they are exactly equivalent
to 'i += 1' and 'j -= 1'. Yet not only do they exist, but if
you run golint over code that contains the assignment versions
it will suggest simplifying them to increment and decrement:
fred.go:4:2: should replace i += 1 with i++
I don't know why Go has decided to go this way, but I do see at least one advantage to using increment and decrement statements instead of assignments: increment and decrement make your intentions clear. Anyone (including yourself) who later reads your code knows that it's not accident or happenstance that you're moving by 1s; it's fully intentional. If there's a bug and this is not the right increment, you may need to look at larger sections of the algorithm, not just change a constant and see if it works; similarly if you now need to move in different strides.
In a related thing, it's also more visually distinctive. Increment
and decrement statements stand out, partly because they don't have
an =, and probably read faster since you don't have to parse the
number when scanning them.
This wouldn't be enough to justify them in a minimal language, but in a pragmatic language like Go I'm glad they exist. Incrementing and decrementing things is common enough that it's nice to have a compact and distinctive idiom that makes your intentions clear.
Sidebar: The operator versus statement distinction here
C has increment and decrement operators. You can use ++ and --
in any context just like other operators, so you can write:
i = j++ * 10 - fred(k++);
And other equally complicated expressions. Often the complications arise with pointers in various contexts.
Go has increment and decrement only as statements, not as operators
(and this is deliberate).
That line is invalid Go; as statements, ++ and -- must occur
on their own, not as part of expressions in assignment statements,
function calls, and so on.