Ruby - problems with user input to integer array

Question

I am trying to accept input of two integers, separated by a space: 3 5 and save that into an integer array. I do this 3 times, but I am having trouble converting this from string to integers. Here is my loop:

for i in 1..3
    puts "What is point " + i.to_s + " ?"    # asks for input
    s.push gets.split(" ")
end

Then, I want to have

if s[1][0] - s[0][0] = 0
    blah blah blah
end

The array s currently looks like

------------
| "1"  "2" |
| "3"  "4" |
| "5"  "6" |
------------

I want it to look like

--------
| 1  2 |
| 3  4 |
| 5  6 |
--------

I have tried gets.split(" ").map { |s| s.to_i } and gets.split(" ").collect{|i| i.to_i} but I realize I should just ask someone here.

I have just started learning Ruby, so if you don't mind a short explanation with the solution, i would really appreciate it :)

Thanks!

Note: This is pretty much the opposite of this question, and I did try to use .collect and .map following the loop, which still did not work.

What is being stored in s? If you are using an older version of ruby, you should try << instead of push, ex: s << gets.split(' '). Your code as it is works as you want it to on my computer. — Adrian
– Adrian, Commented Jul 26, 2010 at 2:08
Currently stored is the array I want, but stored as a strings. I'm using Ruby 1.9.1. ( I also edited original question) — Paul Hoffer
– Paul Hoffer, Commented Jul 26, 2010 at 2:10
I am using 1.9.1 too, and your exact code (with the gets.split(" ").map { |s| s.to_i } instead of just gets.split(" ") is producing arrays of integers. — Adrian
– Adrian, Commented Jul 26, 2010 at 2:13
I got it working now, thank you. That was very strange. I think before I may have had map { |i| i.to_i }, would that have caused it to fail for some reason? I was previously getting undefined method 'to_i' for ["1", "2"]:Array — Paul Hoffer
– Paul Hoffer, Commented Jul 26, 2010 at 2:19

Adrian · Accepted Answer · 2010-07-26 02:20:20Z

2

Okay, sorry, I just saw the mistake. I can't believe I missed that.

In your if statement, you are using = instead of ==. = assigns things, and == compares things. A full working program could look like this:

s = []
for i in 1..3
    puts "What is point " + i.to_s + " ?"    # asks for input
    s.push gets.split(" ").map {|x| x.to_i }
end
if s[1][0] - s[0][0] == 0 # notice the '=='.
    puts 'It worked!'
end

answered Jul 26, 2010 at 2:20

Adrian

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1 Comment

Paul Hoffer Over a year ago

I did fix that after I asked the question, I realized how stupid of me. I had some puts in between which were showing it failing though, so the actual error was separate from that. Thank you for your help though!

Cary Swoveland · Accepted Answer · 2010-07-26 04:52:21Z

1

Your answer looks good to me. You might replace s.push with s << (more Rubyish) and there is no need for split's argument. Though I'm a newbie, I think most Rubyiests would write:

s << gets.split.map {|x| x.to_i}

Also, you could replace

puts "What is point " + i.to_s + " ?"

with

puts "What is point #{i} ?"

answered Jul 26, 2010 at 4:52

Cary Swoveland

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3 Comments

Paul Hoffer Over a year ago

What does << mean? I didn't know I could drop the argument on split. And then it makes sense that I can drop the .chomp too

Cary Swoveland Over a year ago

<< is the append operator. You could write, for example, dog = '' << 'ca' << 'nin' << 'e' => "canine" Note if a = 'ca' and b = 'nine', c = a << b => "canine", but also a => "canine", which may not be what you want. << works similarly with arrays: q = [] << 'quick' << 'brown' << 'fox' => ["quick", "brown", "fox"]

Paul Hoffer Over a year ago

Oh ok. Thanks, that is really good to know! If that isn't what I want, I would just use + instead. Good to know these little things.

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