Ruby String Integer Scanning

Question

Is there a Ruby equivalent of the Java Scanner?

If I have a string like "hello 123 hi 234"

In Java I could do

Scanner sc = new Scanner("hello 123 hi 234");
String a = sc.nextString();
int b = sc.nextInt();
String c = sc.nextString();
int d = sc.nextInt();

How would you do this in Ruby?

This sounds like a half-step. In Ruby, half-steps tend to disappear completely. What do you -want- to do ? — Trevoke
– Trevoke, Commented Jan 19, 2010 at 16:39

klochner · Accepted Answer · 2010-01-19 18:06:41Z

12

Use String.scan:


>> s = "hello 123 hi 234"
=> "hello 123 hi 234"
>> s.scan(/\d+/).map{|i| i.to_i}
=> [123, 234]

RDoc here

If you want something closer to the Java implementation, you can use StringScanner:


>> require 'strscan'
 => true
>> s = StringScanner.new "hello 123 hi 234"
=> # < StringScanner 0/16 @ "hello...">
>> s.scan(/\w+/)
=> "hello"
>> s.scan(/\s+/)
=> " "
>> s.scan(/\d+/)
=> "123"
>> s.scan_until(/\w+/)
=> " hi"
>> s.scan_until(/\d+/)
=> " 234"

edited Jan 19, 2010 at 18:06

answered Jan 19, 2010 at 17:58

klochner

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Comments

Jonas Elfström · Accepted Answer · 2010-01-19 22:12:03Z

7

Multiple assignment from arrays can be useful for this

a,b,c,d = sc.split
b=b.to_i
d=d.to_i

A less efficient alternative:

a,b,c,d = sc.split.map{|w| Integer(w) rescue w}

edited Jan 19, 2010 at 22:12

answered Jan 19, 2010 at 16:38

Jonas Elfström

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8 Comments

Mongus Pong Over a year ago

That would be total genius if Ruby could determine a and c were strings and b and d were integers. Still close enough for me to have learnt something!

Wayne Conrad Over a year ago

In the Java example, the programmer has to know which words are expected to be integers, so there's nothing wrong with a Ruby solution relying upon that requirement. And this -is- prettier than either of my solutions.

Jörg W Mittag Over a year ago

@Pongus: The question already specifies that a and c are strings and b and d are integers, so what's wrong with relying on that?

Wayne Conrad Over a year ago

Wow. That one-liner is just elegant. +1 from me.

Mongus Pong Over a year ago

@Jörg: I didnt mean for it to sound like I was complaining, I would have just been doubly impressed if Ruby had worked that out for us. Still +1. Would have been +2 since the edit if I could. :-)

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