[ruby] How to find a min/max with Ruby

I want to use min(5,10), or Math.max(4,7). Are there functions to this effect in Ruby?

All those results generate garbage in a zealous attempt to handle more than two arguments. I'd be curious to see how they perform compared to good 'ol:

def max (a,b)
  a>b ? a : b
end

which is, by-the-way, my official answer to your question.

In addition to the provided answers, if you want to convert Enumerable#max into a max method that can call a variable number or arguments, like in some other programming languages, you could write:

def max(*values)
 values.max
end

Output:

max(7, 1234, 9, -78, 156)
=> 1234

This abuses the properties of the splat operator to create an array object containing all the arguments provided, or an empty array object if no arguments were provided. In the latter case, the method will return nil, since calling Enumerable#max on an empty array object returns nil.

If you want to define this method on the Math module, this should do the trick:

module Math
 def self.max(*values)
  values.max
 end
end

Note that Enumerable.max is, at least, two times slower compared to the ternary operator (?:). See Dave Morse's answer for a simpler and faster method.

If you need to find the max/min of a hash, you can use #max_by or #min_by

people = {'joe' => 21, 'bill' => 35, 'sally' => 24}

people.min_by { |name, age| age } #=> ["joe", 21]
people.max_by { |name, age| age } #=> ["bill", 35]

You can use

[5,10].min 

or

[4,7].max

It's a method for Arrays.