How to change only elements of one array that are missing in another in Ruby?

Question

If I have 2 arrays, for example a = [1, 2, 3, 4, 5] and b = [4, 7, 9, 1]

and I want to use a method to change elements of the first one. For example

a.map {|x| x.to_s}

but I don't want to change elements that are the same as in the array b. In this case my desire result would be

a = [1, "2", "3", 4, "5"]

1 and 4 are still integers, because the array b has this elements.

So how can I implement this task?

arrays and methods are used just for example to explain what I mean.

jonk · Accepted Answer · 2015-11-25 10:58:53Z

2

you can achieve this with a simple ternary operator inside your map block to either add the respective element as is or as a string depending on whether the second array contains an element with that value:

a.map { |x| (b.include? x) ? x : x.to_s }

edited Nov 25, 2015 at 10:58

answered Nov 23, 2015 at 11:27

jonk

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sawa · Accepted Answer · 2015-11-23 13:29:35Z

1

a.map!{|e| b.include?(e) ? e : e.to_s}

answered Nov 23, 2015 at 13:29

sawa

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1 Comment

Cary Swoveland Over a year ago

...and if the arrays are large, first convert b to a set.

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