> For the complete documentation index, see [llms.txt](https://docs.bcbi.brown.edu/codiac-for-health/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.bcbi.brown.edu/codiac-for-health/computing/julia/numbers-and-math.md).

# Numbers and Math

This page provides syntax for using numbers and mathematic operations in Julia. Each section includes an example to demonstrate the described syntax and operations.

## Types of Numbers <a href="#types_of_numbers" id="types_of_numbers"></a>

* Integer (positive and negative counting number) - e.g., -3, -2, -1, 0, 1, 2, and 3
  * Signed: `Int8, Int16, Int32, Int64, and Int128`
  * Unsigned: `UInt8, UInt16, UInt32, UInt64, and UInt128`
  * Boolean: `Bool` (0 = False and 1 = True)
* Float (real or floating point numbers) - e.g., `-2.14, 0.0, and 3.777`
  * `Float16, Float32, Float64`

Use `typeof()` function to determine type

Input:

```julia
# Define two variables x and y
x = 100
y = 3.14

# Print out the variable types for each
println(typeof(x))
println(typeof(y))
```

Output:

```julia
Int64
Float64
```

## Arithmetic Operators <a href="#arithmetic_operators" id="arithmetic_operators"></a>

| Operator            | Example |
| ------------------- | ------- |
| Addition            | x + y   |
| Subtraction         | x - y   |
| Multiplication      | x \* y  |
| Division            | x / y   |
| Power (Exponent)    | x ^ y   |
| Remainder (Modulo)  | x % y   |
| Negation (for Bool) | !x      |

Input:

```julia
# Demonstrates different math operations
using Printf

n1 = 7    # First number
n2 = 3    # Second number
 
# Output results of different math operations
println("$n1 + $n2 = $(n1 + n2)")             # Addition 
println("$n1 - $n2 = $(n1 - n2)")             # Subtraction 
println("$n1 * $n2 = $(n1 * n2)")             # Multiplication 
println("$n1 / $n2 = $(n1 / n2)")             # Division 
@printf("%d / %d = %.2f\n", n1, n2, n1 / n2)  # Print to 2 decimal places
println("$n1 ^ $n2 = $(n1 ^ n2)")             # Power/Exponent
println("$n1 % $n2 = $(n1 % n2)")             # Modulo/Remainder
```

Output:

```julia
7 + 3 = 10
7 - 3 = 4
7 * 3 = 21
7 / 3 = 2.3333333333333335
7 / 3 = 2.33
7 ^ 3 = 343
7 % 3 = 1
```

## Comparison Operators and Functions <a href="#comparison_operators_and_functions" id="comparison_operators_and_functions"></a>

Input:

| Operator                 | Example                   |
| ------------------------ | ------------------------- |
| Equality                 | x == y or isequal(x, y)   |
| Inequality               | x != y or !isequal (x, y) |
| Less than                | x < y                     |
| Less than or equal to    | x <= y                    |
| Greater than             | x > y                     |
| Greater than or equal to | x >= y                    |

```julia
# compare.jl                                                                                                 
# Demonstrate comparison operators                                                                               

# Assign values to variables using parallel assignment                                                           
c1, c2, c3, c4 = 25, 50, 75, 50
println("c1 = $(c1), c2 = $(c2), c3 = $(c3), c4 = $(c4)")

# Output results of different comparison operations                                                             
 
# Testing equality                                                                                               
println("  c1 = c3 is $(c1 == c3)")
println("  c2 = c4 is $(isequal(c2, c4))")

# Changing values using abbreviated assignment operators                                                        
c1 *= 3    	# Shorthand for c1 = c1 * 3                                                                       
c4 += 1    	# Shorthand for c4 = c4 + 1                                                                       

println("c1 = $(c1), c2 = $(c2), c3 = $(c3), c4 = $(c4)")
 
# Testing less than and greater than
println("  c1 < c2 is $(c1 < c2)")
println("  c4 <= c2 is $(c4 <= c2)")
println("  c1 > c2 is $(c1 > c2)")
println("  c3 >= c2 is $(c3 >= c2)")
```

Output:

```julia
c1 = 25, c2 = 50, c3 = 75, c4 = 50
  c1 = c3 is false
  c2 = c4 is true
c1 = 75, c2 = 50, c3 = 75, c4 = 51
  c1 < c2 is false
  c4 <= c2 is false
  c1 > c2 is true
  c3 >= c2 is true
```

## Exercises

* Create a Health Calculator Using Julia - *<mark style="color:purple;">Forthcoming!</mark>*

## Resources

* Julia Documentation: [Integers and Floating Point Numbers](https://docs.julialang.org/en/v1/manual/integers-and-floating-point-numbers/)
* Julia Documentation: [Mathematical Operations and Elementary Functions](https://docs.julialang.org/en/v1/manual/mathematical-operations/)
* Julia Documentation: [Numbers](https://docs.julialang.org/en/v1/base/numbers/)
* Julia Documentation: [Mathematics](https://docs.julialang.org/en/v1/base/math/)
* Think Julia: [Chapter 1 - The Way of the Program](https://benlauwens.github.io/ThinkJulia.jl/latest/book.html#chap01)


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