MATLAB: Difference between aa && t

if else

Hi I am trying to verify existence of even and odd harmonics in e^(-t) periodic with period pi. For that I try to verify f(t)=f(t+pi). and for f(t+pi) i try to add shift using if-else condition according to this link answer should have even harmonics, http://www.intmath.com/fourier-series/5-harmonic-analysis.php I am trying to solve Example 2(b) in Matlab.
Now if i use the condition 0<=t(i)<pi it shows me even harmonic but if i use 0>=t(i) && t(i)<pi it gives neither even nor odd.
So, my question is why isn't Matlab showing same result for both formats. and which format is correct.

Best Answer

The first form is not going to give you the result you expect, it is equivalent to:
(0 <= t(i)) < pi
Thus, it will compare t(i) to 0, and the result is either 1 (true) or 0 (false). It then compares that 0 or 1 to pi, which is always smaller. Hence the result will always be true.
The second form is the correct one. You can't link comparisons. You have to perform them one at a time and link the results with logical operators.
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