| Author |
Message |
< Erlang ~ String: equal -How to compare input with "[]" ?? |
| andersbranderud |
 Posted: Wed Oct 28, 2009 7:22 pm |
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Joined: 26 Oct 2009
Posts: 2
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Hello!
I am trying to design a function that has as input an list with lists. One sublist can be empty: [] and a sublist can contain " {}" . For example:
[ [], [ {} ], [ {one,1}, {one,0} ] ]
I want this function to append all the arguments in the list. The result should be this: [ {one,1}, {one,0} ]
The functionality of lists: append gives the result: "[{},{one,1},{one,0}]"
Here follows a sub problem in my problem:
I call the following function with this call:
test: append_remove_empty_list ( [ [] ] ).
I want the function to compare X (in the above call "[]") with the string "[]".
Here is the function:
append_remove_empty_list ( [ X | T]) ->
erlang: display (X ),
case string: equal ("[]", "X") of
true -> io: fwrite ("true... \n\n"); %Evaluated true
false -> io:fwrite ("false \n\n")
end.
In the above case the resul in the console window is false, but I want it to be true.
Thanks for your help!
Anders Branderud
bloganders.blogspot.com |
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| uwiger |
| Posted: Thu Oct 29, 2009 12:30 pm |
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User
Joined: 03 Jul 2006
Posts: 604
Location: Sweden
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andersbranderud wrote: Hello!
I am trying to design a function that has as input an list with lists. One sublist can be empty: [] and a sublist can contain " {}" . For example:
[ [], [ {} ], [ {one,1}, {one,0} ] ]
I want this function to append all the arguments in the list. The result should be this: [ {one,1}, {one,0} ]
The simplest way to do this is to flatten the list:
Code: 1> lists:flatten([[], [{}],[{one,1},{one,0}]]).
[{},{one,1},{one,0}]
andersbranderud wrote:
The functionality of lists: append gives the result: "[{},{one,1},{one,0}]"
yes... except for the quotes. When you write something as "..." in Erlang, it means a list of characters, i.e. a string, which is not what you have in this case.
andersbranderud wrote: I call the following function with this call:
test: append_remove_empty_list ( [ [] ] ).
I want the function to compare X (in the above call "[]") with the string "[]".
Here is the function:
Code: append_remove_empty_list ( [ X | T]) ->
erlang: display (X ),
case string: equal ("[]", "X") of
true -> io: fwrite ("true... \n\n"); %Evaluated true
false -> io:fwrite ("false \n\n")
end.
In the above case the resul in the console window is false, but I want it to be true.
The expression Code: case string:equal("[]","X") of...
What you want is to either write Code: case [] == X of true -> ...; false -> ... end
Code:
append_remove_empty_list( [ [] | T]) ->
true;
append_remove_empty_list([ H | T]) ->
false.
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http://www.erlang-consulting.com |
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| andersbranderud |
| Posted: Thu Oct 29, 2009 10:44 pm |
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Joined: 26 Oct 2009
Posts: 2
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Uwiger,
Thanks for your help!
(I knew that this was wrong: case string: equal ("[]", "X") I didn't mean to post that; I intended X without "" )
Have a nice weekend!
Anders Branderud
bloganders.blogspot.com |
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| wuji |
| Posted: Fri Sep 14, 2012 7:30 am |
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Joined: 10 Aug 2012
Posts: 654
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| dongdongwu |
| Posted: Wed Sep 19, 2012 7:48 am |
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Joined: 19 Sep 2012
Posts: 236
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