The three main programming paradigms in widespread use today are:
- Imperative programming
- Functional programming
- Object-oriented programming
Each paradigm has different a different approach to how they solve problems. We are going to go over some concepts that are central to each paradigm. We are also going to implement these constructs from scratch. We are just looking at the semantics of the programming languages. Other aspects of software developement aren't going to be covered here. This includes aspects such as agile vs waterfall vs scrum, or dynamic typing vs static typing.
I have tried to minimize any syntactical differences between the languages. This way, we can focus on the semantical similarities between the languages.
But, what does syntax and semantics mean? A quick explaination is that the semantics of a language is the underlying meaning of a language. For example, in these all have similar semantics:
English greeting
"hello"
Spanish greeting
"hola"
French greeting
"bonjour"
Chinese greeting
"你好"
Syntax is a bit harder to explain. In programming languages, when we talk about syntactical differences, we are mainly talking about superficial differences in how a programming language structures itself. Here are some examples of some made up syntaxes, with the same semantics:
A syntax using Curly brackets
function () { ... }
A syntax based on Mathematics
f(x) = ...
A syntax using keywords
function () do ... end
A syntax using prefix notation
(function () ... )
We are going to present these constructs in javascript, bash and lua.
I recommend checking out the following resources;
javascript: cheatsheet for a 5-10 minute introduction or memory aide. online interpreter, to run javascript code.bash: cheatsheet for a 5-10 minute introduction or memory aide. online interpreter, to run bash code.lua: cheatsheet for a 5-10 minute introduction or memory aide. online interpreter, to run lua code.
The cheatsheets are going to cover stuff that are more specific to each language. We, on the other hand, are going to use the languages to highlight concepts. These concepts are common among several programming languages, not just the ones mentioned here.
The most fundemental feature in the vast majority of programming languages is by far functions. Functions take inputs and output something in return. You probably recognize this from mathematics:
f(x) = sqrt(1+x^2)
In the above example, we assume that both the inputs and outputs are numbers. In programming we regularly work with a far more diverse range of "things". Here's an example:
These functions take as input some text, and return the boolean value True.
Boolean variables can only have one of two values: True or False.
We are going to use this say function in the upcoming examples,
and the True value is going to be especially useful for us in the section "<>".
There we will reimplement the if ... then ... else ... construct using short-circuit which depends on say returning a True value.
if ... else ... then ..., implemented with short circuit evaluation.
Understanding this depends on you also understanding to a certain extent boolean expressions.
So here is a quick recap:
A and B is True if and only if both A and B are True
| input: A | input: B | A and B |
|---|---|---|
| True | True | True |
| True | False | False |
| False | True | False |
| False | False | False |
A or B is True if either A or B are True
| input: A | input: B | A or B |
|---|---|---|
| True | True | True |
| True | False | True |
| False | True | True |
| False | False | False |
In a lot of programming languages AND is represented by &&,
while OR is represented by ||:
Luckily in some programming languages AND is represented by and,
while OR is represented by or:
- Imperative:
- C
- Functional
- JavaScript
- Object oriented
- JavaScript