It is true that ambiguous types cause time-wasting frustration for many a beginner.

The link that Imants gave helps clarify matters:

https://www.haskell.org/tutorial/numbers.html

Even better is the link to the Haskell report given at the end:

https://www.haskell.org/onlinereport/decls.html#default-decls

On Thursday, June 16, 2016, Imants Cekusins <imantc@gmail.com> wrote:
default(Int)

allows to use integers anywhere in this module without specifying their ambiguous type each time, like this: (3::Int)

https://www.haskell.org/tutorial/numbers.html
section 10.4

some other default types may be specified too
somehow I was not aware of this


--
-- Kim-Ee