Map or collect with multidimension arrays

Ruby
#1

What would be the proper call to a multi array either collect or map ?

TIA
Stuart

#2

Hi –

On Sat, 12 Aug 2006, Dark A. wrote:

What would be the proper call to a multi array either collect or map ?

There’s no single proper thing to do; it depends entirely on the task
at hand.

David

#3

David - I’m trying to replicate some of the things in your r4r, but
not using AR just some arrays and or hashes. Maybe it’s the wrong
approach.
As an example

def publishers
editions.map {|e| e.publisher}.uniq
end

Stuart

#4

I dont see anything wrong with that statement.

j`ey
http://www.eachmapinject.com

#5

I know they are interchangeable
But I can’t make it work.

For instance -
x = [[“john”, “doe”],[“mary”,
“jane”],[“jim”,“richards”],['sue",“scott”]]
y = x.map {|i| i + “name” }
p y

It’s returning nil on me ???

Stuart

#6

Hi –

On Sun, 13 Aug 2006, Dark A. wrote:

There’s no single proper thing to do; it depends entirely on the task
x = [[“john”, “doe”],[“mary”, “jane”],[“jim”,“richards”],['sue",“scott”]]
y = x.map {|i| i + “name” }
p y

It’s returning nil on me ???

That should give you an error, because you’re trying to add a string
to an array. Try:

y = x.map {|i| i + [“name”] }

David

#7

[email protected] wrote:

Hi –

On Sat, 12 Aug 2006, Dark A. wrote:

What would be the proper call to a multi array either collect or map
?

There’s no single proper thing to do; it depends entirely on the task
at hand.

DA, note also that map and collect are synonyms. It doesn’t matter
which of
the two you use. :slight_smile:

robert
#8

Dark A. wrote:

def publishers
editions.map {|e| e.publisher}.uniq
end

Regarding your question of when to use #map and when to use #collect, I
think this situation calls for #collect: you’re collecting the
attributes of objects. E.g.

people.collect{|person| person.name }

I use #map when I have more of a “method call” inside the block:

(1…10).map{|i| foo(i) }

That’s at least the convention I follow.

Cheers,
Daniel

#9

Hi –

On Sun, 13 Aug 2006, Morton G. wrote:

It’s returning nil on me ???

Try

x = [[“john”, “doe”],[“mary”, “jane”],[“jim”,“richards”],[“sue”,“scott”]] #
<= “sue” not 'sue"
y = x.map {|i| i << “name” }
p y

The disadvantage of that is that it changes the original objects
inside x.

David

#10

You’re right. Shouldn’t use << in this case. If OP wanted x
modified, then could have just written:

x = [[“john”, “doe”], [“mary”, “jane”], [“jim”,“richards”],
[“sue”,“scott”]]
x.each {|i| i << “name”}

Regards, Morton

#11

Try

x = [[“john”, “doe”],[“mary”, “jane”],[“jim”,“richards”],
[“sue”,“scott”]] # <= “sue” not 'sue"
y = x.map {|i| i << “name” }
p y

Regards, Morton

#12

Just wanted to thank everyone for the help.
No doubt I’ll be back for some other issues :slight_smile:

Stuart