Ruby decrement to limit

Question

I'd like to have a set of methods that can increment/decrement a value, but with a lower limit of zero.

Basically:

def decrement
  @value -= 1
end

Except, I don't want it to go lower than zero.

What's the best "ruby way" to do this?

score 6 · Accepted Answer · answered Mar 01 '11 at 23:23

6

def decrement
  @value -= 1 unless @value.zero?
end

Or if you'd like to throw an exception:

def decrement
  raise RangeError, "can't decrement below zero" if @value.zero?
  @value -= 1
end

answered Mar 01 '11 at 23:23

Paige Ruten

This will fail if `0 < value < 1` – Andrew Marshall Mar 01 '11 at 23:25
Interesting point on the fail case... in this case I'm using integers so I can't hit that fail condition, can I? – Andrew Mar 01 '11 at 23:27
Not if you're using integers. But you simply specified "a value" so I chose not to make assumptions. – Andrew Marshall Mar 01 '11 at 23:28

score 4 · Answer 2 · answered Mar 01 '11 at 23:23

4

def decrement
  @value = [@value-1, 0].max
end

answered Mar 01 '11 at 23:23

dbyrne

This is very clever, but not the most readable at first. However it does seem to avoid the fail case mentioned on yjerem's answer. – Andrew Mar 01 '11 at 23:29
My guess is that its less efficient than your solution as well. I always like providing alternative approaches anyways, since you never know when they might prove useful under different conditions. – dbyrne Mar 01 '11 at 23:38

score 1 · Answer 3 · answered Mar 01 '11 at 23:23

1

def decrement(value)
  value -= 1 if value - 1 >= 0
end

answered Mar 01 '11 at 23:23

Andrew Marshall

score 1 · Answer 4 · answered Mar 01 '11 at 23:32

1

def decrement
  @value -= 1 unless @value - 1 < 0
end

answered Mar 01 '11 at 23:32

Jakub Hampl

4 Answers4