Notes and snippets on Julia lang

notes.jl

#Make a comment just like in Python
#to run > julia testing.jl

#Simple arrays
println("Hello World")
a = [1, 2, 3, 4, 5]

println(a)
b = [1 2 3; 4 5 6; 7 8 9]

println("Array b:", b)

c = ["array", "of", "string"]
println(c)
println(typeof(c))

#Array of functions

trigfuncs = [sin, cos, tan]
print(trigfuncs)
println(typeof(trigfuncs))

#Uninitialized arrays

d = Array{Int64}(undef, 2, 2, 2)
println(d)

#Arrays with mixed types

mixedtypes = [1, "2", 3.0, sin, pi]
typeof(mixedtypes)
println(mixedtypes)


#multidim arrays and matrices

randomArray = rand(2, 2, 2, 2)
println(randomArray)

println("One\t", randomArray[1])
println("Two\t", randomArray[1][1][1])

for n in 1:10 println("Just casually looping through a range\t", n) end

println("==== collect ====")
x = collect(1:10)
println(x)

#Collect with start:step:stop
println(collect(0:10:100))

#Find out the actual step size

println("Finding actual step size: ", step(range(1, length=10, stop=100)))

#Collecting objects from range

println(collect(0:5:100))

for i in collect(1:6)
    println(i)
end

#Generator expressions

println([n^2 for n in 1:5])
println([r * c for r in 1:5, c in 1:5])
println(collect(x^2 for x in 1:10 if x != 1))


#Creating and filling an array

println(zeros(2, 3))
println(ones(2, 3))
println(rand(2, 3))
println(trues(3, 4))
println(fill("DAWG", 2, 2))


#Exclamation mark says that you are about to modify an array with already existing data

println(fill!(a, 42))

println(repeat([1, 2, 3], 2))

# Creating similar arrays - getting the same shape

b = similar(a)

a = rand(0:10,10, 10)

#reshaping arrays

id  = reshape([1, 2, 3, 4], 2, 2)
println(id)

#Max numbers

println(max(1, 2, 3))


#Julia Type System

println("Supertype of Number is " , supertype(Number))
#println("Subtypes of Number are ", subtypes(Number)) - y u no work?

println(sizeof(BigFloat))

#
# function showtypetree(T, level=0)
#     println("\t" ^ level, T)
#     for t in subtypes(T)
#         if t != Any
#             showtypetree(t, level+1)
#         end
#    end
# end
#
# showtypetree(Number)

isodd(1000003) && @warn("That's odd!")

name = "wat"
if name == "Julia"
   println("I like Julia")
elseif name == "Python"
   println("I like Python.")
   println("But I prefer Julia.")
else
   println("I don't know what I like")
end

for i in 0:10:100
    println(i)
end

for color in ["red", "green", "blue"] # an array
    print(color, " ")
end


for i in 1:10
    @show i
end


# To remember the value of a variable outside of the for loop scope it needs to be marked as global
for i in 1:10
 global howfar
 if i % 4 == 0
    howfar = i
 end
end

#Comprehensions

#"Let S be the set of all elements n where n is greater than or equal to 1 and less than or equal to 10"
S = Set([n for n in 1:10])
println(S)


#When in need of working with two or god knows how many arrays there is an option to zip'em
#Over and under supply is handled.

for i in zip(0:10, 100:110, 200:210)
    println(i)
end

#In order to iterate through an array with an index,
A = zeros(10, 1)
for i = 1:length(A)
   @show i
end


#While loops

while true
   println(x)
   x += 1
   x >= 4 && break
end