~/Types of Programming Languages

Brandon Rozek

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PhD Student @ RPI studying Automated Reasoning in AI and Linux Enthusiast.

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Array Languages

Array programming languages generalizes operations on scalars to apply transparently to vectors, matrices, and higher-dimensional arrays.

Example Language: R

In R everything is by default a vector, typing in

x <- 5

Will create a vector of length 1 with the value 5.

This is commonly used by the scientific and engineering community. Other languages include MATLAB, Octave, Julia, and the NumPy extension to Python.

Constraint Programming Languages

A declarative programming language where relationships between variables are expressed as constraints. Execution proceeds by attempting to find values for the variables that satisfy all declared constraints.

Example: Microsoft Z3 Theorem Prover

(declare-const a Int)
(declare-fun f (Int Bool) Int)
(assert (> a 10))
(assert (< (f a true) 100))
(check-sat)

Command Line Interface Languages

Commonly used to control jobs or processes

#!/bin/bash
echo "hello, $USER. I wish to list some files of yours"
echo "listing files in the current directory, $PWD"
ls  # list files

Concurrent Languages

Languages that support language constructs for concurrency. These may involve multi-threading, distributed computing, message passing, shared resources, and/or future and promises.

Example: Erlang

ping(0, Pong_PID) ->
    Pong_PID ! finished,
    io:format("ping finished~n", []);

ping(N, Pong_PID) ->
    Pong_PID ! {ping, self()},
    receive
        pong ->
            io:format("Ping received pong~n", [])
    end,
    ping(N - 1, Pong_PID).

pong() ->
    receive
        finished ->
            io:format("Pong finished~n", []);
        {ping, Ping_PID} ->
            io:format("Pong received ping~n", []),
            Ping_PID ! pong,
            pong()
    end.

start() ->
    Pong_PID = spawn(tut15, pong, []),
    spawn(tut15, ping, [3, Pong_PID]).

Data-oriented Languages

These languages provide powerful ways of searching and manipulating relations.

Example: SQL

SELECT * FROM STATION
WHERE 50 < (SELECT AVG(TEMP_F);

Give all the information from stations whose average temperature is above 50 degrees F

Declarative Languages

Declarative languages express the logic of a computation without describing its control flow in detail

Example: SQL again

The example code above doesn’t tell the computer how to perform the query, just what you want.

Functional Languages

Style of computer programs that treat computation as the evaluation of mathematical functions and avoid changing-state and having mutable data.

primes = filterPrime [2..] 
  where filterPrime (p:xs) = 
          p : filterPrime [x | x <- xs, x `mod` p /= 0]

Imperative Languages

The use of statements to change a program’s state

Example: C

#define FOOSIZE 10
struct foo fooarr[FOOSIZE];

for(i = 0; i < FOOSIZE; i++)
{
  do_something(fooarr[i].data);
}

Iterative Languages

Languages built around or offering generators

Example: Python

def countfrom(n):
    while True:
        yield n
        n += 1
        
g = countfrom(0)
next(g) # 0
next(g) # 1

List-based Languages -LISPs

Family of programming languages with a history of fully parenthesized prefix notation.

Example: Common Lisp

 ;; Sorts the list using the > and < function as the relational operator.
 (sort (list 5 2 6 3 1 4) #'>)   ; Returns (6 5 4 3 2 1)
 (sort (list 5 2 6 3 1 4) #'<)   ; Returns (1 2 3 4 5 6)

Logic Languages

Programming paradigm based on formal logic. Expressions are written stating the facts and rules about some problem domain.

Example: Prolog

mother_child(trude, sally).
 
father_child(tom, sally).
father_child(tom, erica).
father_child(mike, tom).
 
sibling(X, Y)      :- parent_child(Z, X), parent_child(Z, Y).
 
parent_child(X, Y) :- father_child(X, Y).
parent_child(X, Y) :- mother_child(X, Y).

?- sibling(sally, erica).
 Yes

Symbolic Programming

A programming paradigm in which the program can manipulate its own formulas and program components as if they were plain data.

Example: Clojure

Clojure is written in prefix notation, but with this macro, you can write in infix notation.

(defmacro infix
  [infixed]
  (list (second infixed) 
        (first infixed) 
        (last infixed)))

Probabilistic Programming Language

Adds the ability to describe probabilistic models and then perform inference in those models.

Example: Stan

model {
	real mu;
	
	# priors:
	L_u ~ lkj_corr_cholesky(2.0);
	L_w ~ lkj_corr_cholesky(2.0);
	to_vector(z_u) ~ normal(0,1);
	to_vector(z_w) ~ normal(0,1);
	
	for (i in 1:N){
		mu = beta[1] + u[subj[i],1] + w[item[i],1] 
			+ (beta[2] + u[subj[i],2] + w[item[i],2])*so[i];
           rt[i] ~ lognormal(mu,sigma_e);        // likelihood
      }
}

Quick Summary of Programming Paradigms

Imperative

Declarative

Symbolic Programming