On Fri, 27 Oct 2006, Josef Svenningsson wrote:
My argument for intercalate builds on the fact that intersperse seems to be the wrong abstraction. Recall that I supplied some evidence that intersperse is only used together with concat: http://www.google.com/codesearch?q=file%3A%5C.hs+intersperse&btnG=Search+Code
Except for pretty printing, intersperse always comes together with concat.
I can tell you at least two non-concat applications of 'intersperse'. 1. Transforming a power series for 'f' to the onw for '\x -> f(x^2)' is simply 'intersperse 0'. 2. Upsampling a signal as needed for wavelet transform. However, you can argue that these applications are special cases of inserting (n-1) zeros between list items in order to multiply the length by a factor of n, and thus 'intersperse' doesn't scale well for this purpose.