Types

Haskell is a statically typed language, which means (among other things) that the compiler knows statically — before and without the need to execute a piece of source code — what its type is.

In the REPL, you can obtain this information with the special :t meta-instruction (instructions starting with a colon and a letter are typically instructions directed towards the REPL and only valid there).

For example, we can ask: what is the type of the literal True?

ghci> :t True
True :: Bool 

The REPL responds that the expression True has type (::) Bool

.

(In general, Haskell places types "after". This is similar to Python, Scala, TypeScript, and many other languages; but different than C and Java, in which types generally are placed "before", for example in the signature of functions.)

A character literal is written within single quotes. What is the type of 'a'?

(Just answer with the type, not the full REPL output.)