Can You Count Infinitely in Ruby Using a Case Statement?

Question

I'm trying to calculate what happens if the total score averages out above 100. I'm currently using a case statement to output the different scores. Would be the optimal solution to express the range above 100, allowing us to output 'A+++'.

def get_grade(score_1, score_2, score_3)
  total = (score_1 + score_2 + score_3)/3

  case total
  # What if the score is above 100? 
  # I want it to express 'A+++'
  when 90..100 then 'A'
  when 80..89 then 'B'
  when 70..79 then 'C'
  when 60..69 then 'D'
  else             'F'
  end
end

p get_grade(91, 97, 93) # => 'A'
p get_grade(52, 57, 51) # => 'D'
p get_grade(105, 106, 107) # => 'A++'

I prefer @Nic's solution, but you could add either of the following lines to the case statement: `when 101..Float::INFINITY then 'A+++'` or `when 101..total then 'A+++'`. — Cary Swoveland, Jul 29 '16 at 00:17

Nic Nilov · Accepted Answer · 2019-08-20T10:12:52.620

6

That would be a typical case for the else clause. Why not rework your case statement to look like this, assuming each score argument is non-negative:

case total
  when 90..100 then 'A'
  when 80..89 then 'B'
  when 70..79 then 'C'
  when 60..69 then 'D'
  when 0..59 then 'F'
  else 'A+++'
end

edited Aug 20 '19 at 10:12

answered Jul 28 '16 at 20:58

Nic Nilov

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I thought about that for sure; I just didn't know if there was another way to do so using INFINITY or anything else? Thanks! – Louis Magnotti Jul 28 '16 at 21:01
You could, but Ruby does not define a constant like `Fixnum::MAX`. Figuring out the actual value would be a little too involved, like [here](https://gist.github.com/pithyless/9738125) or [here](http://stackoverflow.com/a/736313/2116518). Therefore it's probably better to stick to a simple solution. – Nic Nilov Jul 28 '16 at 21:06
@NicNilov what about user passes one or more negative numbers as argument (which makes total < 0)? – marmeladze Jul 28 '16 at 21:14

Ruby Racer · Answer 2 · 2016-07-28T21:08:34.010

4

You may combine methods and use comparisons

...
else
    if total > 100
        "A+++"
    else
         "F"
    end
end

If you want to play a little, you could change the case statement to:

(total > 100) ? "A+++" : "FFFFFFDCBAA"[(total/10).to_i]

edited Jul 28 '16 at 21:08

answered Jul 28 '16 at 21:00

Ruby Racer

5,690
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score 2 · Answer 3 · answered Jul 28 '16 at 21:08

2

You can provide a proc to the case to allow you to use an expression like > 100

def get_grade(score_1, score_2, score_3)
  total = (score_1 + score_2 + score_3)/3

  case total
  # What if the score is above 100? 
  # I want it to express 'A+++'
  when 90..100 then 'A'
  when 80..89 then 'B'
  when 70..79 then 'C'
  when 60..69 then 'D'
  when ->(n) { n > 100 } then 'A+++'
  else 'F'
  end
end

answered Jul 28 '16 at 21:08

max pleaner

26,189
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1

That's a nice use of lambda but it kinda duplicates the semantics of the `case` statement. – Nic Nilov Jul 28 '16 at 21:23

Simply Beautiful Art · Answer 4 · 2017-11-21T15:07:53.577

0

Here's a nifty solution using infinity:

first mentioned by @CarySwoveland

case total
  when 101..Float::INFINITY then 'A+++'
  when 90..100 then 'A'
  when 80..89 then 'B'
  when 70..79 then 'C'
  when 60..69 then 'D'
  else 'F'
end

edited Nov 21 '17 at 15:07

answered Nov 21 '17 at 13:20

Simply Beautiful Art

1,284
15
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Can You Count Infinitely in Ruby Using a Case Statement?

4 Answers4