Feature #9808: Enumerable#argmin_by, #argmax_by

• Status: Rejected
• Assignee: -
• Target version: -

[prijutme4ty (Ilya Vorontsov)]

What about introducing Enumerable #argmin_by (and #argmax_by too, of course) method?
Use cases are wide from mathematical problems to a general tasks. Here are two very simple examples:

(1..2).step(0.01).argmin_by{|x| Math.sin(x)*x}

queues = [[],[],[],[]]
# ...
least_busy_queue = queues.argmin_by{|queue| queues.size }
least_busy_queue << new_task

For cases when #argmin_by isn't enough because one need to obtain index of minimal element I suggest #index_min_by method which returns index of element for which block yields minimal value. It prevents user from using ineffective but straight two-pass algorithm like arr.index(arr.min):

# guess the number game
hidden_number = rand(100)
player_answers = 5.times.map{ gets.to_i }
best_player = player_answers.index_min_by{|answer| (answer-hidden_number).abs}

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Status changed from Open to Feedback

Could you explain what it does?

[prijutme4ty (Ilya Vorontsov)]

I'm sorry for this issue. It looks, I've misunderstood and underestimated #min_by functionality. I think issue can be closed.

[Eregon (Benoit Daloze)]

• Status changed from Feedback to Rejected