I found precedence and associativity is a big obstacle for me to understand what the grammar is trying to express at first glance to haskell code.
For example,
A good rule of thumb seems to be that you can never make a custom operator that has precedence over built in syntactic constructs. For instance consider this example:
if b then f *** x else f *** y
Regardless of the associativity of ***
, no one would expect it to binds as:
(if b then f *** x else f) *** y
There aren't a lot of syntactic constructs in Haskell (do
and case
are a little special because of layout syntax) but let
can be used as another example:
(let x = y in y *** x) /= ((let x = y in y) *** x)