Why the author claims this function call not to be a recursive call?

Question

The author claims that the next call is not a recursive call, but I don't get why.

Source: http://courses.cms.caltech.edu/cs11/material/haskell/lectures/haskell_lecture_5.pdf

Answer 1

The code is recursive (it is defined in terms of itself). I believe that @leftroundabout's idea about the emphasis being on function is accurate. The next slide says that

do putY (y - x)
   gcdST

is

Recursive data definition
* not recursive function call
* like ones = 1 : ones

I.e. there is no recursive function call because gdcST is not a function (it takes no argument!). This is a recursive data definition.