Julia as a calculator

The Julia command line

Julia REPL behaves almost similar to general scientific or engineering calculators. In most cases, Julia accepts input style which people are familiar to.

Using constants and variables

We can use identifiers, constants, variables, and function in Julia coding as well as Julia REPL

• const let us define our own constants
  • \ enables display built-in constants with their symblos
  • Julia binds number and variables, does not assign. A variable that has a number can be bound to a new number.
  • Julia supports literal coefficient, by tab completion (see table below).

x = 3
2 * x = 6
2x = 6

Different number types and their bit length in Julia

Julia provides various types of numbers

• Integer: default bit length of Julia is 'signed 64-bit (Int64).'
  • Julia does not automatically pick a number type large enough to hodl the result of an arithmetic operation (overflows).
  • Julia defaults to showing all signed numbers in decimal format and unsigned numbers, such as UInt8, in hexadecimal format.

Floating-point numbers

• The default size is 64 bit, which means each floating-point number consumes 8 bytes of memory

Defining functions

• Functions use constants and arguments.
• Functions can be saved in a .jl file.

r = 4.5
V = 4*pi*r^3/3  # V=381.7035... r is the argument, and V will be recalculated as r changes
foo(x, y, z) = 2x + 4y - z  # x, y, z are arguments that consist of the function foo

# Volume calculations, consider that the code below is saved as 'volumes.jl'
sphere_volume(r)        = 4*pi*r^3/3  # r is argument
cylinder_volume(r, h)   = pi*r^2*h    # r, h are arguments

# In julia REPL
include("volumes.jl")
cylinder_volume(1, 2)
6.2831...

How to use numbers in practice

Keep in mind the below

• Just use the default integer and floating-point sizes. Only consider smaller or larger numbers when performance or the nature of your problem demands it.
  • Prefer signed integers to unsigned. It is very easy to make a mistake using unsigned numbers.