integral calls the function with a vector x, you're expecting x to be a scalar in your haar function. E.g:
>> [1 2 3] && 1
The easiest thing for you to do is to modify haar to use logical indexing on val:
function val = haar(x)
val = zeros(size(x)); % assume zero
val(0<=x & x<0.5) = 1; % set ones
val(0.5<=x & x<1) = -1; % set -1s
end
