Flow

if, elif, else

The conditional statement looks like Python. An if line, a condition, a colon, and an indented body.

if score >= 90:
    print("great")
elif score >= 50:
    print("ok")
else:
    print("try again")

Three rules:

• The condition must be a Bool. A number like if score: won't compile. Use if score != 0: or if Bool(score): instead.
• There can be any number of elif branches, including none. else is optional.
• elif and else must be indented at the same column as their if. The compiler checks this.

A complete example:

def grade(score: Int32) -> NoneType
    if score >= 90:
        print("great")
    elif score >= 50:
        print("ok")
    else:
        print("try again")
    return

def main() -> Int32
    grade(95)
    grade(60)
    grade(20)
    return 0

Variables and branches

If a variable is declared inside a branch and you want to use it afterwards, declare it in every branch. The compiler merges the values. This rule is explained with a working example on the Variables page.

Division by zero at compile time

When the compiler can see that you're dividing by the constant zero, it rejects the code before running it:

x: Int32 = 1 / 0   # compile error

This applies to /, //, and %. If the divisor comes from somewhere the compiler can't check, like user input, the check happens at runtime instead, and only in debug mode. Without debug mode it's undefined behavior.

Recursion

A recursion example:

def fact(n: Int32) -> Int32
    if n <= 1:
        return 1
    return n * fact(n - 1)

def main() -> Int32
    print(fact(5))
    return 0

Deep recursion can hit stack limits, so keep the depth sane. Loops are a planned feature, listed in the Limits page.