Trying to split a string (ruby)

Question

I'm new to Ruby. I'm trying to make some simple calculator program. So, basically what it's supposed to do is you input something like 4+2 and it outputs 6. Simple, right? So I thought. I'm trying to split a string at all the operation characters, so I made this quick regex thinking it would work. It didn't.

class Calculator 
def add(a,b)
    return a+b
end
def sub(a,b)
    return a-b
end
def div(a,b)
    return a/b
end
def mul(a,b)
    return a*b
end
end

operation = gets.split("[\/\+\-\*]")
print(operation)
sleep()

the sleep() is there to pause the console so I can take a look at my outputs. But right now, it's outputting ["4+2\n"]?? I don't know what I'm doing wrong. I need some help. (it should output ["4","+","2"]). Thanks in advance.

hwnd · Accepted Answer · 2013-11-24 15:07:57Z

2

You don't need to escape every character inside of your character class. Consider the following:

operation = gets.gsub(/[^\d\/*+-]/, '').split(/([\/*+-])/)

or

operation = gets.split(/([\/*+-])/).map(&:strip)

edited Nov 24, 2013 at 15:07

answered Nov 24, 2013 at 3:20

hwnd

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1 Comment

pguardiario Over a year ago

Yes, but use \d instead of 0-9

Shawn Balestracci · Accepted Answer · 2013-11-24 02:58:38Z

1

For a regular expression you want to use / instead of ":

operation = gets.split(/[\/\+\-\*]/) # ["4", "2\n"]

There's an extra newline remove that with strip:

operation = gets.strip.split(/[\/\+\-\*]/) # ["4", "2"]

But we lost the operator. Looking at the docs for split:

If pattern contains groups, the respective matches will be returned in the array as well.

Adding () in our regex creates a group. So then we have:

operation = gets.strip.split(/([\/\+\-\*])/) # ["4", "+", "2"]

answered Nov 24, 2013 at 2:58

Shawn Balestracci

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3 Comments

hexagonest Over a year ago

thanks so much, but I don't understand the gets.strip.split. I understand that it strips the newline, but shouldn't it be gets.split(whatever).strip?

Shawn Balestracci Over a year ago

Split returns an array. strip operates on the string, I'm removing the newling before calling split.

pguardiario Over a year ago

-1 learn what to escape in regex before posting regex answers.

uncutstone · Accepted Answer · 2013-11-24 03:35:57Z

0

You can try the following code.

operation = gets.chomp.gsub(/[\/\+\-\*]/, ';\0;').split(";")
print(operation)

Execution result:

4+2/3*9-0
["4", "+", "2", "/", "3", "*", "9", "-", "0"]

edited Nov 24, 2013 at 3:35

answered Nov 24, 2013 at 3:29

uncutstone

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