Does String#scan(/(..)(..)/) produce an array of arrays?

ruby-talk
1

Hi All,

“Programming Ruby” says the following for String#scan at http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_string.html#String.scan:

a = “cruel world”

…

a.scan(/(…)(…)/) » [[“cr”, “ue”], ["l ", “wo”]]

I wrote the following to test whether scan actually produced an array or arrays:

a = "cruel world"
ar = a.scan(/(…)(…)/)
puts “Type of ar = %s of size %d” % [ar.class, ar.size]
ix=0
ar.each {|x| puts “Type of ar[#{ix}] is %s” % [ix, ar[ix].class]; ix+=1}

That resulted in:

Type of ar = Array of size 2
Type of ar[0] is 0
Type of ar[1] is 1

So it seem like we don’t have an array of arrays. So what do we have? Or am I all wet?

Regards,
Richard

A programmer is a device for turning coffee into code.
Jeff Prosise (with an assist from Paul Erdos)

2

RLMuller wrote:

Hi All,

“Programming Ruby” says the following for String#scan at
Programming Ruby: The Pragmatic Programmer's Guide

a = “cruel world” |

…|

a.scan(/(…)(…)/) |» |[[“cr”, “ue”], ["l ", “wo”]]|

I wrote the following to test whether scan actually produced an array
or arrays:|

a = “cruel world”
ar = a.scan(/(…)(…)/)
puts “Type of ar = %s of size %d” % [ar.class, ar.size]
ix=0
ar.each {|x| puts “Type of ar[#{ix}] is %s” % [ix, ar[ix].class]; ix+=1}

That resulted in:|

Type of ar = Array of size 2
Type of ar[0] is 0
Type of ar[1] is 1|

So it seem like we don’t have an array of arrays. So what do we have?
Or am I all wet?|

You’re all wet. :wink:

Seriously, you’ve just made a typo or two. Your last format string does
an interpolation instead of using a format specifier. You’re printing
the value of ix as the class.

I suggest each_with_index and consistent formatting, like

ar.each_with_index {|x,ix| puts “Type of ar[#{ix}] is #{ar[ix].class}” }

If you don’t like variable interpolation, you can use a real printf:

printf “Type of ar[%d] is %s\n”,ix,ar[ix].class

Anyhow, you do get real live arrays here, just as the Book says.

Hal

3

Many thanks, Hal,

As I told you before, I’ve got your book, but digesting everything in
a book of 579+ pages takes time, as does finding the answer to a
specific question, so thanks for hanging out on this newsgroup.

And thanks for ‘drying me out’; I certainly was ‘all wet’ in my
amateurish mistake. Better still, I’m thankful for your truly
Rubyesque improvement. I learned one more thing, thereby.

Regards,
Richard