or-function with switch

Question

Tor Fredrik Hove 2011-10-15

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https://ww2.mathworks.cn/matlabcentral/answers/18381-or-function-with-switch

采纳的回答： Walter Roberson

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Can you not use or in one of the cases for switch. I tried here but it did not call it at all:

http://bildr.no/view/1000983

I know about the case {2, 3} possibility just wondered about if or is a possibility here

here is my function:

function grade=switchletgrade1(quiz)

if quiz<0 ||quiz>4

grade='X'

else

switch quiz
 case 3 || 2
 grade='B'
 case 4
 grade='A'
        otherwise
 grade='C'
end

end

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Answer 1

Walter Roberson 2011-10-15

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No, 3||2 cannot be used in that context. Each case list is executed (unless the switch matched earlier), so 3||2 as a case label is evaluated as logical(3)||logical(2) which is true||true which is true which has the numeric value 1. Coding 3||2 as a case is thus equivalent to coding a 1 at that point.

The {} notation is the one you need for multiple possibilities.

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Tor Fredrik Hove 2011-10-15

here i have tried with || it seems like case just ignores it. Does what you say by saying true mean that it uses it like other functions does excecute from true after an if? If so what is the case with this excecution that I did here:

http://bildr.no/view/1001313

Jan 2011-10-15

Please, Tor, post the code instead of screenshots.

"case 2||3" is equivalent to "case true", because "2||3" is equivalent to "logical(2)||logical(3)".

You want: "case {2, 3}". Reading the documentation is stringly recommended: "doc switch" and the Getting Started chapters.

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Answer 2

William 2011-10-15

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It works. You had one too many "end" statements. You might want to make it a little bit more stable by using more "=<" statements in the switch statement otherwise a 3.4 is going to be a "C"

function grade=switchletgrade1(quiz)
if quiz<0 ||quiz>4
 grade='X'
else
      switch quiz
          case 3 || 2
          grade='B'
          case 4
          grade='A'
          otherwise
          grade='C'
      end
  end

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Walter Roberson 2011-10-15

Tor does *not* have too many 'end' statements. Refer to the documentation for "function", which says,

You can terminate any type of function with an end statement, but doing so is not required unless the file containing the function also contains one or more nested functions. Within this file, every function (including primary, nested, private, and subfunctions) must be terminated with an end.

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