switch with "ignore case" -> switchi

Question

Thomas Becker 2017-7-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/348339-switch-with-ignore-case-switchi

评论： Jan 2017-7-12

Just a question or a proposal for an enhancement:

Has anyone ever wondered, why there isn't an enhanced switch-function for ignoring the case of strings, like strcmp/strcmpi, regexp/regexpi. It would be just consistent to have a switchi function.

Currently, you always have to program this problem using switch lower(xxx) and change all cases to lower letters..

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jan 2017-7-12

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/348339-switch-with-ignore-case-switchi#answer_273811

编辑：Jan 2017-7-12

在 MATLAB Online 中打开

switch can operate on numerical data also. Then a "switchi" is not meaningful and would lead to ambiguities:

if rand < 0.5
  x = 'Hello';
else
  x = 9;
end
switch x
  case 'Hello', disp('hello');
  case 9,       disp('9');
end

In my opinion switch lower(x)) is clear and clean. If x is created anywhere far apart in the code, "switchi" would be misleading, because it requires additional assumptions about the contents of the argument.

By the way: The public forum is not the right location to post an enhancement request. Use the official MathWorks account instead, see the "Contact Us" link on this page.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Thomas Becker 2017-7-12

Hi Jan,

when reading your answer, this seems to be the reasons for not having a switchi command. Thanks a lot for your very fast answer.

请先登录，再进行评论。

Answer 2

Walter Roberson 2017-7-12

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/348339-switch-with-ignore-case-switchi#answer_273817

编辑：Walter Roberson 2017-7-12

The case labels are technically expressions rather than constants, so you can also wrap them in lower() calls instead of changing their content.

On the other hand, if you go into Preferences to Keyboard => Shortcuts, you can add a shortcut for "Change to Lower Case", which you would probably use by highlighting the text and giving the shortcut sequence. That might be easier than typing lower() around each of the labels.

I find that in practice I do not tend to use switch() very often, and certainly not with enough cases to make changing the labels to lowercase to be an issue. Instead I find that in the circumstances where someone might typically use a switch(), that I instead use data structures that contain both the text and the control information about what to do, and then it is a matter of applying a small analysis function to figure out the offset into the table and pulling out the control information and executing it.

3 个评论
显示 1更早的评论隐藏 1更早的评论

Thomas Becker 2017-7-12

Thanks for your hint for using more shortcuts - always appreciated!

I don't use switch too often, either, but a collegue does very frequently, and he asked me for tricks to simplify it. Good idea with using data structures instead!

Jan 2017-7-12

在 MATLAB Online 中打开

A switch with a bunch of cases is nicer than a stack of elseif branches:

switch lower(Command)
  case 'start'
  case 'stop'
  case 'forget'
  case 'relax'
  otherwise  % No SWITCH without OTHERWISE!
    error('Programming error: Unexpected Switch expression!');
end
if strcmpi(Command, 'start')
elseif strcmpi(Command, 'stop')
elseif strcmpi(Command, 'forget')
elseif strcmpi(Command, 'relax')
else % No ELSEIF stack without ELSE!
    error('Programming error: Unexpected ELSEIF branch!');
end