before typeclass 101
theorem about add and count
exercise till "nonzero" part
prove nonzeros_app
typeclass 101 - descriptions for some common used typeclass
type signature
examples for Eq and Ord
make Show instance manually
create instance for Read
make instance of Enum
type class Bounded
play with Num
play with Profunctor. impl Num btw
syntax in functions
pattern matching - changing file name
suppress warnings
guards guards
a little more about guards
"where"
Merge branch 'software-foundations'