juliatut3.txt

Julia Tut Part 3
For/While Loops and other expressions

Iterating
FOR Loops
through an array
for i in array
  do something
end

ex. for y in [a,b,c]
      y = y * 2
      println(y)
    end

iterating over range

for j=start:end
  println(j)
end

ex. for j=1:25
      println(j)
    end

WHILE Loops
i = y
while condition
  do something
  modify i
end

ex. i = 1
    while i<=5
      println(i)
      i+=1
    end

Continue
can be used with conditions to move through the loop
ex.
for i in 1:5
  if i%2 == 0
    continue
  end
  println(i*i)
end
will print 1, 9 and 25 because it skips 2 and 4

Break
Similar, will break when meets condition
for i in 1:5
  if i==4
    break
  end
  println(i*i)
end
will print 1, 4 and 9, stopping when it gets to 4

Compound Expressions
BEGIN
Can be used to describe a block
ex.
area = begin
  base = 10
  height = 5
  1/2*(base*height)
end
will evaluate to 25.0

can also write the same methods using ";"
ex.
area = base = 10; height = 5; 1/2*(base*height)


Tasks
Defined in producer consumer problems
One complex procedure is generating values and another is consuming them
Consumers cant just call producers because they might not be ready
So we use taks
produce() -> returns a value
consume() -> Once a producer is wrapped in a task, consume can be
            called on that obj

ex.
function producer()
  produce("start")
  for n=1:4
    produce(2n)
  end
  produce("stop")
end;

p = Task(producer)
#can call repreatedly
consumer(p) -> "start"
consumer(p) -> 2
.....
cosume(p) -> "stop"
consume(p) -> ()

ex. fibonacci


function fib()
  a = 0
  produce(a)
  b = 1
  produce(b)
  while true
    a,b = b, a+b
    produce(b)
  end
end

p = Task(producer)

consumer(p) -> 0
consumer(p) -> 1
.....
cosume(p) -> "inf"

Can also run stuff
ex.
for i in Task(fib)
  prinln(i)
  if i > 15
    break
  end
end

will evaluate to
0
1
1
....
21

Can also have more details
function fib(msg)
  println(msg)
  a = 0
  produce(a)
  b = 1
  produce(b)
  while true
    a,b = b, a+b
    produce(b)
  end
end

p=@task fib("hollo World")
when consumed will print out
"Hello World"
0
1
1
....
inf

Generators can use less memory and are useful for quick processing

EXCEPTIONS
You don't always want your code to pass through or throw standard errors
So you can use try catch

try
  attempt something
catch
  do something
end

ex.
try
  "hi" + 345
catch
  println("W O W")
end

will print "W O W" because an error is raised

That marks the end of the youtube tutorials.
Everything I add from here will be from diffrent sources.