Control Flow

Control Structures in Helix

Control flow in Helix combines familiar constructs with expressive syntax and modern additions like pattern matching.

Helix currently supports:

if-else
while loops
for loops
match expressions (pattern matching similar to switch)
break and continue
return

If / Else

The if expression allows conditional execution of code blocks.

A simple if statement looks like this:

if x > 0 {
    print(x);
}

if blocks can be stacked in order to make a decision tree, using the else keyword like this:

let score = 85;

if score > 90 {
    print("Excellent");
} else if (score > 75) {    //as noted earlier, condition brackets are optional
    print("Good");
} else {
    print("Keep trying");
}

While

The while expression can be used to loop through statements while a given condition(s) returns true.

A simple while loop looks like this:

let x = 0;

while x < 3 {
    print(x);
    x++;
}

For

for loops essentially let you iterate over a range

A simple helix for loop looks like this:

for var i:i32 = 0; i < 100; i++ {
    print(i);
}

Additionally, even here, you could use traditional condition brackets, like:

for (var i:i32 = 0; i < 100; i++){
    print(i);
}

Multiple initializations or increments can be done at once using a comma , (multiple conditions are achieved by using logical operators like && or ||) :

for (var i:i32 = 0, var j:i32 = 3; i < 100; i++, j--){
    print(i)
}

If you are looping over any array, string, map, or any compatible list-like structure, helix has a range clause:

for letter in word {
    print(word[letter]);
}

Match

Due to match having a lot of extra features on it, we made a completely separate page for it. To learn more, refer to the Match Guide

Break/continue

break and continue in helix serve the same purpose they do in other languages.

break is used to exit a loop

let count = 0;

for letter in sentence{
    if letter == ' ' {
        break;    //breaks the loop after the first word in the sentence is iterated over
    }
    count++;
}

print(count);   //prints the length of the first word

continue skips the current iteration and moves to the next one.

let count = 0;

for letter in sentence {
    if letter == ' ' {
        continue;  //skips spaces and continues with the next character
    }
    count++;
}

print(count);    //prints the length of the sentence excluding whitespaces

Return

return is used to exit a function and pass a value back to the caller of the function

fn square(x:i32) -> i32 {
    return x * x;
}

let result = square(5);
print(result);

References

Match Learn about the range of features offered by the match statement(helix's version of switch)