Table of Contents
Preface
There is a saying about these two concepts: imperative programming (Imperative programming) emphasis on what we do how, and declarative programming (Declarative programming) emphasize what we do what.
Can take a practical example as follows, a couple comes to the restaurant, the waiter wants to ask where they sit, they will answer:
- Command direction (Imperative, how): I see the other table is empty and close to the window, the place has a nice view, so my husband and I will sit there.
- Declaration direction (Declarative, what): Give me a table of 2.
We may notice that when giving the declaration, there is usually a hidden imperative. For example, when calling a table with 2 people, this couple assumed that the waiter knew which table to choose and how to guide their guests to that table.
SQL and HTML examples
SELECT * FROM Users WHERE Country='Vietnam';
<article>
<header>
<h1>Declarative Programming</h1>
</header>
</article>
As we can see, in both languages we are more concerned with what will be output what, don’t care about them how to produce that result.
Declared programming vs functional programming
Functional programming (Functional programming) Can be considered a sub-branch of declarative programming, in functional programming, we also give the problem to the computer to solve. (the what), but at the same time also give a solution (like how), it’s just that we don’t do anything to change the value / state of the variables.
We will familiarize ourselves with this model in the following sections.
Typical language of each type
- Command language (Imperative): Fortran, Algol, Pascal, C / C ++, Java
- Declaration language (Declarative):
- Logic language: Prolog
- Functional language (Functional): LISP, APL, ML, FP, Haskell, F #
Hope this helps!
