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Difference between revisions of "Records"

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(Added a link to Erlang.org.)
(Added with and without defaults; Added how to modify a record.)
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== Defining Records ==
 
== Defining Records ==
 +
 +
=== Without Defaults ===
 +
 +
Defining a record in code looks like this:
  
 
<code>
 
<code>
 
-record( recordname, { element1, element2, element3 } ).
 
-record( recordname, { element1, element2, element3 } ).
 
</code>
 
</code>
 +
 +
Defining one in the interpreter looks like this:
 +
 +
<code>
 +
rd(recordname, {element1, element2, element3}).
 +
</code>
 +
 +
=== With Defaults ===
  
 
== Creating a Record ==
 
== Creating a Record ==
 +
 +
Defining a record in code looks like this:
  
 
<code>
 
<code>
R = #recordname{ element1 = "One", element2 = 2, element3 = three }.
+
-record( recordname, { element1 = "One", element2 = 2, element3 = three } ).
 +
</code>
 +
 
 +
Defining one in the interpreter (what I did to create these examples) looks like this:
 +
 
 +
<code>
 +
rd(recordname, {element1 = "One", element2 = 2, element3 = three }).
 
</code>
 
</code>
  
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<code>
 
<code>
 
elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8.
 
elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8.
 +
</code>
 +
 +
== Modifying a Record ==
 +
 +
<code>
 +
2> R1 = #recordname{}.  % Uses the defaults.
 +
#recordname{element1 = "One",element2 = 2,element3 = three}
 +
3> R2 = R1#recordname{ element1 = "Two" }.  % Only modify one part of the record.
 +
#recordname{element1 = "Two",element2 = 2,element3 = three}
 
</code>
 
</code>
  

Revision as of 11:43, 15 July 2007

Contents

Defining Records

Without Defaults

Defining a record in code looks like this:

-record( recordname, { element1, element2, element3 } ).

Defining one in the interpreter looks like this:

rd(recordname, {element1, element2, element3}).

With Defaults

Creating a Record

Defining a record in code looks like this:

-record( recordname, { element1 = "One", element2 = 2, element3 = three } ).

Defining one in the interpreter (what I did to create these examples) looks like this:

rd(recordname, {element1 = "One", element2 = 2, element3  = three }).

Matching a Record

elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8.

Modifying a Record

2> R1 = #recordname{}.  % Uses the defaults. 
#recordname{element1 = "One",element2 = 2,element3 = three}
3> R2 = R1#recordname{ element1 = "Two" }.  % Only modify one part of the record.
#recordname{element1 = "Two",element2 = 2,element3 = three}

More Information

More information at http://erlang.org/doc/getting_started/records_macros.html#5.3.