String Case

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Revision as of 21:51, 3 September 2006 (edit)
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Ayrnieu (Talk | contribs)
(remove httpd_util use (does this even work? I don't have this module); replace with simple ASCII solution and advice on beyond-ASCII)
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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!)+For ASCII, you can do it yourself in this simple manner:
-<code> +<code>
-1> httpd_utils:to_upper("hello").+to_upper(S) -> lists:map(fun char_to_upper/1, S).
-"HELLO"+to_lower(S) -> lists:map(fun char_to_lower/1, S).
-2> httpd_utils:to_lower("ERLANG").+char_to_upper(C) when C >= $a, C =< $z -> C bxor $\s;
-"erlang"+char_to_upper(C) -> C.
 +char_to_lower(C) when C >= $A, C =< $Z -> C bxor $\s;
 +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.  
 +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:
 +
 +<code>
 +-module(unicode).
 +
 +-record(unicode_string,{encoding,language,data}).
 +</code>
[[Category:CookBook]][[Category:StringRecipes]] [[Category:CookBook]][[Category:StringRecipes]]

Revision as of 09:17, 25 September 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}).
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