Idiomatic Printing an array with commas

Ruby
1

Hi,

I want to print an array (of strings, mostly) with commas separating the
elements (so it would look like the result in the irb

a =[one,two,three]
printspecial a # should produce “[one, two, three]” not “onetwothree”
as it # currently does

I tried a.map{|s| s.to_s + ", "
but this gives me [one, two, three,]
with an extra comma trailing the last element

Is there a nice ruby idiom to do what I want (or to simply produce the
necessary string for printing?

Or, do I have to resort to an explicit loop checking for the last
element and not alter it?

2

Chuck B. wrote:

I want to print an array (of strings, mostly) with commas separating the
elements (so it would look like the result in the irb

You want String#inspect. (irb calls #inspect on the object it’s
displaying)

$ irb --simple-prompt

a = [“one”,“two”,“three”]
=> [“one”, “two”, “three”]

puts a.inspect
[“one”, “two”, “three”]
=> nil

3

I tried it and that appears to be exactly what I need!!

Thank you very much!!!

Brian C. wrote:

You want String#inspect. (irb calls #inspect on the object it’s
displaying)

$ irb --simple-prompt

a = [“one”,“two”,“three”]
=> [“one”, “two”, “three”]

puts a.inspect
[“one”, “two”, “three”]
=> nil

4

On 2010-06-13 11:30:40 -0700, Chuck B. said:

I tried a.map{|s| s.to_s + ", "
but this gives me [one, two, three,]
with an extra comma trailing the last element

Is there a nice ruby idiom to do what I want (or to simply produce the
necessary string for printing?

Or, do I have to resort to an explicit loop checking for the last
element and not alter it?

If you want it to “look like the result in the irb”, you want
Array#inspect.

5

Chuck B. [email protected] writes:

Hi,

I want to print an array (of strings, mostly) with commas separating the
elements (so it would look like the result in the irb

[snip]

Is there a nice ruby idiom to do what I want (or to simply produce the
necessary string for printing?

a = [“one”, “two”, “three”]
puts a.inspect
puts “[” + a.join(", ") + “]”

>> [“one”, “two”, “three”]

>> [one, two, three]

6

On Sun, Jun 13, 2010 at 1:30 PM, Chuck B. [email protected]
wrote:

I tried a.map{|s| s.to_s + ", "

As other people have pointed out, you are looking for the inspect
method. If
you are wanting to print it
p a
puts a.inspect

are the same thing.

As far as your issue with the comma after the last element, the join
method
will do what you were trying to do with map, except it won’t put it on
the
last element.

a.join(', ') # => “1, 2, 3”

7

You can always try a * ", "

% irb --simple-prompt

a = [“a”,“b”,“c”]
=> [“a”, “b”, “c”]

a * ", "
=> “a, b, c”

8

“.inspect”, “.join”, “*”. Of course, there isn’t just one way to get
the job done in Ruby!

I appreciate all the tips

Thanks,

Chuck

9

On 2010-06-17 20:08:32 -0700, Chuck B. said:

“.inspect”, “.join”, “*”. Of course, there isn’t just one way to get
the job done in Ruby!

I appreciate all the tips

Thanks,

Chuck

Well, Array#inspect makes use of behavior identical to that of
Array#join. You could* implement it as:

class Array
def inspect
‘[’ << map{|item| item.inspect}.join(', ') << ‘]’
end
end

Also, Array#join and Array#* are synonyms. So there’s way closer to one
way than to many. :wink:

**

Rubinius source-diving is a great way to find out a Ruby reference
implementation for something written in C in MRI or YARV Rubies.