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Difference between revisions of "String Case"

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== Solution ==
 
== Solution ==
Use httpd_util:to_upper or httpd_util:to_lower from the OTP httpd_util module. (Yes, I know that these would make more sense in the string module!)
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For ASCII, you can do it yourself in this simple manner:
<code>  
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<code>
1> httpd_utils:to_upper("hello").
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to_upper(S) -> lists:map(fun char_to_upper/1, S).
"HELLO"
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to_lower(S) -> lists:map(fun char_to_lower/1, S).
2> httpd_utils:to_lower("ERLANG").
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char_to_upper(C) when C >= $a, C =< $z -> C bxor $\s;
"erlang"
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char_to_upper(C) -> C.
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char_to_lower(C) when C >= $A, C =< $Z -> C bxor $\s;
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char_to_lower(C) -> C.
 
</code>
 
</code>
 
The httpd_util module contains a dog's breakfast of functionality that probably belong in other modules, but that have not been added due to backwards-compatibility concerns.
 
  
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For many other languages where case-change makes sense, you can extend the above in a simple manner by adding new ranges or specific characters to the char_to_*/1 functions.  For some, you may need extra processing in to_upper/1 or to_lower/1.
  
[[Category:CookBook]]
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Erlang doesn't have a nice unicode-respectful way of doing this.  If you'd like to prototype such a way, you might start with:
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<code>
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-module(unicode).
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-record(unicode_string,{encoding,language,data}).
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</code>
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[[Category:CookBook]][[Category:StringRecipes]]

Revision as of 09:47, 23 November 2006

Problem

You need to convert a string to all uppercase or all lowercase.

Solution

For ASCII, you can do it yourself in this simple manner:

to_upper(S) -> lists:map(fun char_to_upper/1, S).
to_lower(S) -> lists:map(fun char_to_lower/1, S).
char_to_upper(C) when C >= $a, C =< $z -> C bxor $\s;
char_to_upper(C) -> C.
char_to_lower(C) when C >= $A, C =< $Z -> C bxor $\s;
char_to_lower(C) -> C.

For many other languages where case-change makes sense, you can extend the above in a simple manner by adding new ranges or specific characters to the char_to_*/1 functions. For some, you may need extra processing in to_upper/1 or to_lower/1.

Erlang doesn't have a nice unicode-respectful way of doing this. If you'd like to prototype such a way, you might start with:

-module(unicode).

-record(unicode_string,{encoding,language,data}).