Loops and Conditionals

Overview

Questions

• What basic loop constructs does Julia offer?
• What is the syntax for conditionals in Julia?

Objectives

• SOME OBJECTIVE

We only cover two basic loop types here: while and for loops, and both are similar to most other programming languages.

while loops

while loops in Julia look like this:

JULIA

while <condition>
    <do something>
end

For example, the following prints the first few squares:

JULIA

> n = 0
> while n < 5
      println(n^2)
      n += 1
  end

for loops

for loops in Julia do look similar to those in Python:

JULIA

for <variable> in <iterable>
    <do something>
end

The equvalent for loop to the previous example for a while loop would look like this:

JULIA

> for n in 0:4
      println(n^2)
  end

<iterable> can be anything that can be iterated over and <variable> will, one by one, take values from that iterable, e.g., an array.

Conditionals

using if

The probalbly most-used syntax for a conditional in programming uses the if keyword and Julia does the same. The general syntax of an if conditional is as follows:

JULIA

if <condition 1>
    <do something>
elseif <condition 2>
    <do something else>
else
    <do something entirely different>
end

The blocks elseif and else are optional, also as usual.

using the ternary operator

Conditionals can also be written differently in a number of other programming languages, using ternary operators, like this:

JULIA

a ? b : c

which is equivalent to

JULIA

if a
    b
else
    c
end

Note that ? binds rather strongly, so usually you will have to enclose the expression within parentheses:

JULIA

(4 > 0) ? "larger than 0" : "equal to or less than zero"