map or collect with multidimension arrays

[Dark Ambient]

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

TIA
Stuart

 

[dblack]

Hi --

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

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[Robert Klemme]

Hi --



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.

robert

 

[Dark Ambient]

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

Hi --

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

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[Dark Ambient]

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

 

[dblack]

Hi --

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

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 ????

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

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[Daniel Schierbeck]

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

 

[Morton Goldberg]

Try

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

Regards, Morton

 

[dblack]

Hi --

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 ????

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

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[Morton Goldberg]

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

Hi --

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 ????

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

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[Dark Ambient]

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

Stuart

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

Hi --

On Aug 12, 2006, at 11:08 AM, Dark Ambient wrote:

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 ????

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

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.