#Calc of Talbot PAtterns
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N=21
d=2.0
sigma=1.0
cospart(x,n) = cos ( ( pi*n/(2*sigma))*(n - 2*x/d) )
sinpart(x,n) = sin ( ( pi*n/(2*sigma))*(n - 2*x/d) )
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sumcos(x,n) = (-N<n) ? ( cospart(x,n) + sumcos(x,n-1) ):0
sumsin(x,n) = (-N<n) ? ( sinpart(x,n) + sumsin(x,n-1) ):0
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I(x)=(sumcos(x,N))**2 + (sumsin(x,N))**2
plot [-5:5] I(x)