FP 2013 Course
- Introduction
This course online: http://kspt.icc.spbstu.ru/2013/course/lang
Why should we study various programming languages?
Why is there no universal language sufficient for all tasks?
Important qualities of the code:
- It would work
- It should be easy to read/understand/debug
- It should be easy to modify/re-use/extend
- It should be fast/resource-efficient
Core ideas of functional programming:
- Pure functions without side effects
- Immutable data
- Functions are first-class citizens
- Erlang Basics
Read the first chapters of "Learn You Some Erlang for Great Good!": from "Starting Out" till "Recursion".
- Recursion and Lists Handling
We start with recursion vs iteration (recursion.erl).
Why it is impossible to use loops like while and for in Erlang?
How can recursion replace iteration?
We continue with different ways of defining linked lists, including the standard Erlang lists (list_handling.erl). Then we write some functions over lists and discuss the method of structural recursion.
- Higher-order Functions
We start with a task for the students to create a Java function that transforms an IPv4 address that is given a list of integers into its canonical string representation. The task continues with IPv6 addresses (IpAddressUtil.java, IpAddressUtilTest.java).
Why do we need unit tests?
The obvious idea is to copy and paste the IPv4 version and start modifying it.
Why copy-pasting code is a bad idea?
Name some flaws in the initial imperative implementation, see
IpAddressUtil.ipV4ToString().
The students then suggest to create a single
ipToString(List<Integer> parts, boolean isIpV4) function that
does IPv4 or IPv6 conversion depending on a boolean flag. Why is
it a bad idea? What re-usable parts do we get from this change?
Next we step back and create a higher-level description of the transformation algorithm:
- First we transform each number in the address into its string representation (decimal or hexadecimal or whatever)
- Then we join the results using the specified separator (dot or semicolon or something else)
What we see here is two more general operations:
- Transform each element of the list using some transformation (it should be a function, but we cannot use functions as function parameters in Java, so it should be an interface with a single method)
- Join a list of strings using a separator (useful for joining lists of things via ", " as enumerations or "\n" as lines)
These functions have nothing to do with IP addresses: the first is
a general map() function on lists, and the second is a join()
function on strings.
See the final versions of our IP to string functions.
- HOFs on Lists
TODO: See hof.erl
06-07. Henderson-Escher Example
TODO: See henderson.erl