Conditions and loops

Summary

Conditional structures
Loops

Conditional structures

The IF condition

The first condition is “if”. It evaluates a boolean expression and executes the code if this condition is true. The code is skipped if the condition is false.

if 3+3 == 6 {
    // your code goes here
}

The ELSE condition

The second condition is “else”. It can only be used after if or elif and marks the end of a conditional structure. It executes the code only if the expression evaluated by the previous condition was false.

if 3+3 == 7 {
    // your code goes here
} else {
    // your code goes here
}

The ELIF condition

The third condition is “elif”, which is a contraction of “else if”. It is a combination of both conditions. It can only be used after if or another elif, but a conditional structure cannot start with elif.

var x: i32 = 3 + 3;
if x == 5 {
    // ...
} elif x == 6 {
    // ...
} else {
    // ...
}

is the equivalent of

var x: i32 = 3 + 3;
if x == 5 {
    // ...
} else {
    if x == 6 {
        // ...
    }
    else {
        // ...
    }
}

Loops

The FOREVER loop

The first loop is forever. It keeps executing the same code block forever and never stops unless if you force it to.

forever {
    // ...
}

The WHILE loop

The second loop is while. It keeps executing the same code block while a condition is true and stops when it becomes false.

var x: i32 = 0;
var y: i32 = 5;

while x <= y {
    x += 1;
}

The UNTIL loop

The third loop is until. It is the opposite of while, because it keeps executing the same code block while a condition is false and stops when it becomes true.

var x: i32 = 0;
var y: i32 = 0;

until x == y {
    x += 1;
}

Note: in Shard, we prefer using this loop but we also provide while if you want.

The FOR loop

The last loop is for. It first declares a variable, which is local (it cannot be used outside of the loop) then checks a condition and does something at the end.

for var i: i32 = 0; i <= 5; i += 1 {
    // ...
}

is equivalent to

{
    var i: i32 = 0;
    while i <= 5 {
        i += 1;
    }
}

How to exit a loop

To exit a loop, just use the break keyword.

How to return at the beginning of a loop

To return at the beginning of a loop and skip what comes next in the loop, use the continue keyword.