http://www.perlmonks.org?node_id=447701


in reply to The Concept of References

That looks like an explaination of pointers. It strongly suggests that you can do arithmetic on references, to get to the "next" memory location. I like this image: 
           +--------+       
Alias:     | $alias | ------------+
           +--------+             |                          
                                  |
                                 \|/
           +--------+       +----------+       +---------+
Variable:  |  $var  | ----> | Variable | ----> | Content |
           +--------+       +----------+       +---------+
                                 /|\                   
                                  +--------+          
           +--------+       +----------+   |          
Reference: |  $ref  | ----> | Variable | --+          
           +--------+       +----------+

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But that might be too much internals for some.

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Re^2: The Concept of References
by Juerd (Abbot) on Apr 14, 2005 at 12:25 UTC

    These things are often called name, container and value. Your diagram has them neatly put in columns: 

    
             Name            Container           Value


           +--------+       
Alias:     | $alias | ------------+
           +--------+             |                          
                                  |
                                 \|/
           +--------+       +----------+       +---------+
Variable:  |  $var  | ----> | Variable | ----> | Content |
           +--------+       +----------+       +---------+
                                 /|\                   
                                  +--------+          
           +--------+       +----------+   |          
Reference: |  $ref  | ----> | Variable | --+          
           +--------+       +----------+

    [download]
    The "variable" label isn't accurate, though, if you also call one of the blocks "variable". And, to more clearly illustrate that an alias is absolutely not a reference, you could consider making the original name and the second name more visually equal: 
    +--------+ __
| $name  |   \
+--------+    \      +-----------+       +-------+
               ====> | container | ----> | value |
+--------+    /      +-----------+       +-------+
| $alias | __/
+--------+

    [download]
    And I think the content/value part of Reference is missing in your diagram. It does have one, and that is the actual reference! Hard to draw, though.

    Juerd # { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }

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[d/l]
[select]
      I know how references work internally, but those are details not really needed to understand references and aliases. As for visually equalizing $name and $alias, I usually do the diagram interactively, in front of a blackboard, starting with the middle line of my diagram. And then I won't wipe out the $name box to draw it a bit lower (or higher).
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Re^2: The Concept of References
by leriksen (Curate) on Apr 15, 2005 at 02:27 UTC
    Nice diagram - I deliberately didnt do it this way, even though yours is more accurate. And I hope to add The Concept of Alias' today.

    ...it is better to be approximately right than precisely wrong. - Warren Buffet

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