Logical statement with variable gates and true/false vectors without using EVAL

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Jurgens Wolfaardt 2017-10-31

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评论： Jurgens Wolfaardt 2017-10-31

Hi All! Thank-you for help in advance.

I have a long logical statement of a dozen true/false vectors with eleven logical gates between them. The gates can have any one of the three values selected from:

gate = {'&','|','&~'};

Let me use just two vectors and one gate for simplicity. If I use eval, it is a simple matter of concatenating a string...

tfvect1 = [0;1;0;1;1];
tfvect2 = [1;1;1;1;0];
gate = {'&','|','&~'};
n=1;
tf_result = eval(['tfvect1',gate{n},'tfvect2'])

but I want to avoid EVAL (aka 'EVIL') because I want to compile the code. This is actually the first time ever I've used EVAL, but I can't think of another way. STR2FUNC doesn't interpret a logical statement as valid, that is:

tfvect1 = [0;1;0;1;1];
tfvect2 = [1;1;1;1;0];
gate = {'&','|','&~'};
str='@(hit1,hit2,n)hit1 gate{n} hit2'
tf = str2func(str);
tf(tfvect1,tfvect1,1)

chokes on the logical statement (which MATLAB is happy with if you type it on the command line) - apparently STRFUNC only accepts algebraic statements.

Surely there is a better method than hard coding all the possible permutations of the logical statement? Any ideas please?

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Jurgens Wolfaardt 2017-10-31

在 MATLAB Online 中打开

Thank-you Walter! Do you mean..

tfvect1 = [0;1;0;1;1];
tfvect2 = [1;1;1;1;0];
gate = {'&','|','&~'};
tf = str2func(sprintf('@(hit1,hit2,n)hit1 %s hit2', gate{n}))
tf(tfvect1,tfvect1,2)

It gives me the same result regardless of 'n' used

Walter Roberson 2017-10-31

Sorry, the code is not parameterized by n. You would need different code for full expansion.

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Answer 1

Sean de Wolski 2017-10-31

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/364343-logical-statement-with-variable-gates-and-true-false-vectors-without-using-eval#answer_288743

在 MATLAB Online 中打开

How about indexing into the function handles?

gate = {@and, @or, @(x,y)x&~y} %'&','|','&~'};
tfvect1 = [0;1;0;1;1];
tfvect2 = [1;1;1;1;0];
gateidx = [2 3 1];
for ii = numel(gateidx):-1:1
    tf(:, ii) = gate{gateidx(ii)}(tfvect1, tfvect2);
end

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Jurgens Wolfaardt 2017-10-31

Oops - its the latter!

Jurgens Wolfaardt 2017-10-31

Thanks all - this taught me heaps.

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Answer 2

Walter Roberson 2017-10-31

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/364343-logical-statement-with-variable-gates-and-true-false-vectors-without-using-eval#answer_288742

在 MATLAB Online 中打开

possible_gates = {'&','|','&~'};
andnot = @(a,b) a &~ b;
gatefuns = {@and, @or, andnot};
[~, gateidx] = ismember(gate, possible_gates);
current = gatefuns{gateidx(1)}(tfvect{1}, tfvect{2});
for K = 3 : length(tfvect);
  current = gatefuns{gateidx(K-1)}(current, tvfect{K});
end