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Difference between revisions of "Records"

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(Added with and without defaults; Added how to modify a record.)
(Added how to get a value out of a record.)
(2 intermediate revisions by one user not shown)
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[[Category:Concepts]]
 
== Defining Records ==
 
== Defining Records ==
  
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=== With Defaults ===
 
=== With Defaults ===
 
== Creating a Record ==
 
  
 
Defining a record in code looks like this:
 
Defining a record in code looks like this:
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rd(recordname, {element1 = "One", element2 = 2, element3  = three }).
 
rd(recordname, {element1 = "One", element2 = 2, element3  = three }).
 
</code>
 
</code>
 +
  
 
== Matching a Record ==
 
== Matching a Record ==
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elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8.
 
elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8.
 
</code>
 
</code>
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 +
== Getting the value of a record element ==
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 +
<code>
 +
1> R1 = #recordname{}.  % Uses the defaults.
 +
#recordname{element1 = "One",element2 = 2,element3 = three}
 +
2> io:format("~p~n", [R1#recordname.element1]). % prints "One"
 +
"One"
 +
ok
 +
</code>
 +
  
 
== Modifying a Record ==
 
== Modifying a Record ==
  
 
<code>
 
<code>
2> R1 = #recordname{}.  % Uses the defaults.  
+
3> R2 = #recordname{}.  % Uses the defaults.  
 
#recordname{element1 = "One",element2 = 2,element3 = three}
 
#recordname{element1 = "One",element2 = 2,element3 = three}
3> R2 = R1#recordname{ element1 = "Two" }.  % Only modify one part of the record.
+
4> R3 = R2#recordname{ element1 = "Two" }.  % Only modify one part of the record.
 
#recordname{element1 = "Two",element2 = 2,element3 = three}
 
#recordname{element1 = "Two",element2 = 2,element3 = three}
 
</code>
 
</code>
 +
  
 
== More Information ==
 
== More Information ==
  
 
More information at [http://erlang.org/doc/getting_started/records_macros.html#5.3 http://erlang.org/doc/getting_started/records_macros.html#5.3].
 
More information at [http://erlang.org/doc/getting_started/records_macros.html#5.3 http://erlang.org/doc/getting_started/records_macros.html#5.3].

Revision as of 10:48, 27 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

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.

Getting the value of a record element

1> R1 = #recordname{}.  % Uses the defaults.
#recordname{element1 = "One",element2 = 2,element3 = three}
2> io:format("~p~n", [R1#recordname.element1]). % prints "One"
"One"
ok


Modifying a Record

3> R2 = #recordname{}.  % Uses the defaults. 
#recordname{element1 = "One",element2 = 2,element3 = three}
4> R3 = R2#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.