Cosmo/docs/control.md

Control statements

Control statements are used to control program flow. Using logical expressions, different branches of code will be run.

if statements

The syntax for if statements in cosmo looks like:

if 1 == 1 then
    // true branch here
    print("true")
else
    // false branch here
    print("false")
end

true

the elseif keyword can also be used to have an else conditional branch:

if false then
    print("bye")
elseif true then
    print("hi")
end

hi

while loops

While loops are basic "repeat while X is true" loops. Their syntax consists of the while keyword, followed by the logical expression and the do keyword. The loop body is ended by the matching end keyword. In practice this looks like:

while true do
    print("oh no! infinite loop!")
end

oh no! infinite loop!oh no! infinite loop!oh no! infinite loop!...

for loops

There are two main types of for loops, the traditional c-style for loops, and the for-each loop which requires an iterator object (see objects.md)

The c-style for loops starts with the for keyword, followed by '(' and an initializer, a conditional expression, and an iterator statement each separated by a ';', followed by ')' then the do keyword. The loop body is ended by the matching end keyword. Like so:

var total = 0
for (var i = 0; i < 10; i++) do
    total = total + i
end
print(total)

45

The for-each loops are a little different, the absence of the starting '(' marks it as a for-each loop. After the for keyword, the values expected during iteration are expected, each separated by a ','. After that, the in keyword is expected and the iterator object is expected. The loop body is ended by the matching end keyword. The start of the loop body is marked by the do keyword. Like so:

for key, val in ["hello", "world"] do
    print("[" .. key .. "] = " .. val)
end

[0] = hello [1] = world

Tables have a built-in iterator in the VM and are accepted in for-each loops. However, iterations over tables are not guaranteed to be in any specific order.