Why Does This Definition of a Piecewise Function Produce a Warning Message?
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Kareem Elgindy
on 31 Jan 2022
Commented: Kareem Elgindy
on 2 Feb 2022
MATLAB issues a warning when defining the below piecewise function
syms y(x); y(x) = piecewise(x<1, x+1, 1<=x<2, x-1);

But when I write
y(x) = piecewise(x<1, x+1, (1<=x) & (x<2), x-1);
the warning message disappears. Could someone point to an example where those two ways of defining a piecewise function produce different results? It seems here that they give identical results.
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Accepted Answer
Benjamin Thompson
on 31 Jan 2022
This is just a warning about good programming syntax. Good programming style is to never leave order of operations in doubt, and add parenthesis where needed to clarify order of operations. While a <= b <= c is good mathematical notation, it may no be clear to a compiler or interpreter how the expression must be evaluated.
3 Comments
Benjamin Thompson
on 2 Feb 2022
>> -3 <= -2 < -1
ans =
logical
0
>> (-3 <= -2) & (-2 < -1)
ans =
logical
1
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