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You mean Haskell has things besides lists???
It’s important to focus on data structures, since getting your data
right is step 1 to great Haskell code.
Generic data structures
There are three basic flavors to the data structures
- Sequences: list, vector, ByteString, Text, and Seq (not covered)
- Order of values matters
- Can have multiple copies of the same value
- Maps: Map, HashMap, IntMap
- Map a key to a value
- Aka, dictionary
- Each key only appears once
- Sets: Set, HashSet, IntSet
- Map without values
- Like a sequence, but (1) order undefined and (2) no duplicates
- Each of these families has very similar APIs (though not quite
- Learning one will help you master the others.
- Yes, this means you already know most of the vector, ByteString,
and Text APIs.
- The Map and Set APIs are also very similar.
- APIs are designed to be imported qualified (lots of conflicting
- Later: we’ll look at mono-traversable for typeclasses to unify these APIs.
- Lists are fully lazy
Text still have strict chunks
- Boxed vectors are spine strict
Map has strict and lazy modules, different impacts on values
- Unboxed and storable vectors are fullhy strict.
Impacts: undefined, infinite structures, performance, memory usage.
- Unlike the other sequences, ByteString and Text are monomorphic
- There are three common flavors of Vector, we’ll cover the
- IntMap and IntSet requires Int keys
- Some of the structures have constraints on keys or values
There are also ByteString and Text builders for efficient
Quiz: Pick the data structure
- Names of all students in a class
- Names and grades of all students in a class
- All the prime numbers
- The first 1000 prime numbers
- Whitelist of allowed email addresses to access a resource
We’ll come back to this quiz after we explore the data types in more