Is there a method to limit/clamp a number?

Question

I wrote the following code, which keeps x within the range (a..b). In pseudo code:

(if x < a, x = a; if x > b, x = b)

In Ruby it would be something like:

x = [a, [x, b].min].max

As it is quite basic and useful function, I was wondering if there is a native method to do that in ruby.

As of Ruby 2.3.3 there is apparently no method like this, what would be the shortest/more readable way to do it?

I found:

x = [a, x, b].sort[1]

so far, but I'm not sure if it is more readable.

Just a matter of interest, from for exactly native function? — ted, Aug 18 '12 at 17:47
You've answered your own question there - nice use of the sort function. I don't think you'll get much more readable than that. — xiy, Aug 18 '12 at 18:20
you problably mean: `x2 = [a, [x, b].min].max`. It looks ok to me, use basic generic methods to build the rest. — tokland, Aug 18 '12 at 22:16
Interesting use of sort.. makes the whole thing independant of the order.. — Karthik T, Dec 10 '13 at 10:25
I love your cryptic version. You should put it in as an answer so I can up vote it. — drewish, Feb 26 '14 at 21:35
@drewish Thanks. I found it somewhere (in the R communauty if I remember well). A create an answer — mb14, Feb 27 '14 at 14:40

score 61 · Accepted Answer · edited Jan 06 '17 at 08:07

61

Ruby 2.4.0 introduces Comparable#clamp:

523.clamp(0, 100)        #=> 100

edited Jan 06 '17 at 08:07

Drenmi

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answered Aug 18 '12 at 23:13

Marc-André Lafortune

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The best part: the reason ruby has no clamp method is they can't stop arguing about what to name the function. – Mar 23 '15 at 23:15
This has finally been added now. – fgb Sep 01 '16 at 18:29
2

Haha, I implemented Comparable#clamp. Took them long enough to merge my patch... ;-) – nerdinand Sep 22 '16 at 21:10

score 37 · Answer 2 · answered Feb 27 '14 at 14:39

37

My own answer : NO

However

x = [a, x, b].sort[1]

Is a solution.

answered Feb 27 '14 at 14:39

mb14

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Not gonna lie, that's sexy. – henrebotha Apr 08 '15 at 13:17
3

I think this might be the single prettiest line of code I've ever seen. – Nic Mar 14 '16 at 17:22
2

The cool thing is that the order in which you put the min, max and x does not even matter. – Fritzz Oct 28 '16 at 12:26

Zeddy · Answer 3 · 2014-02-07T20:52:46.740

12

I did this:

class Numeric
  def clamp min, max
    [[self, max].min, min].max
  end
end

So whenever I want to clamp anything, I can just call:

x.clamp(min, max)

Which I find pretty readable.

edited Feb 07 '14 at 20:52

answered Feb 07 '14 at 20:10

Zeddy

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score 0 · Answer 4 · answered Nov 18 '17 at 03:08

Here is my solution which borrows heavily from the actual implementation:

unless Comparable.method_defined? :clamp
  module Comparable
    def clamp min, max
      if max-min<0
        raise ArgumentError, 'min argument must be smaller than max argument'
      end
      self>max ? max : self<min ? min : self
    end
  end
end

score -1 · Answer 5 · answered Jul 26 '16 at 14:06

-1

The most appealing solution for now in my opinion is the sort option:

[min,x,max].sort[1]

When you don't mind monkey patching existing core classes. I think the range class is a good candidate for a clamp method

class Range
  def clamp(v)
    [min,v,max].sort[1]
  end
end

(min..max).clamp(v)

Or the plain array object. I don't like this, because the clamp function only is correct for 3 element arrays

class Array
    def clamp
      sort[1]
    end
end

You can call it like this:

[a,x,b].clamp

answered Jul 26 '16 at 14:06

gamecreature

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Calling clamp over an array or a range seems to be really deceiving. That is not a result someone would think about. Monkey patching numeric or comparable looks like something easier to understand IMHO. – Ulysse BN Aug 22 '18 at 09:43

Is there a method to limit/clamp a number?

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