Control Flow

Kite provides standard control flow constructs: if/else, while loops, and for loops.

If Statements

Basic Syntax

if condition {
    // body
}

With Parentheses

Parentheses around the condition are optional:

// Both are valid
if (x > 5) {
    doSomething()
}
if x > 5 {
    doSomething()
}

If-Else

if condition {
    // true branch
} else {
    // false branch
}

Examples

var x              = 10
if x > 5 {
    var result     = "greater"
}
if (x              == 10) {
    var result     = "equal"
} else {
    var result     = "not equal"
}
// Nested conditions
if x > 0 {
    if x < 100 {
        var result = "in range"
    }
}

Important: Braces Required

Unlike some languages, Kite requires braces for if/else bodies:

// Valid
if x > 5 { doSomething() }
// Invalid - missing braces
if x > 5 doSomething()  // ERROR

While Loops

Basic Syntax

while condition {
    // body
}

Examples

var count = 0
while count < 10 {
    count++
}
// With parentheses (optional)
while (count < 20) {
    count++
}

For Loops

Iterating Over Ranges

for i in 0..5 {
    // i = 0, 1, 2, 3, 4 (end exclusive)
}

Iterating Over Arrays

var items   = ["a", "b", "c"]
for item in items {
    // item = "a", "b", "c"
}

With Index

var items    = ["a", "b", "c"]
for index, item in items {
    // index = 0, item = "a"
    // index = 1, item = "b"
    // index = 2, item = "c"
}

For Loops with Resources

For loops can create multiple resources:

var environments = ["dev", "staging", "prod"]
[for env in environments]
resource S3.Bucket bucket {
    name         = "data-${env}"
}

This creates three buckets: data-dev, data-staging, data-prod.

Array Comprehensions

Kite supports three forms of array comprehensions.

Form 1: Compact (Inline Body)

// Basic
[for i in 0..6: i * 2]
// Result: [0, 2, 4, 6, 8, 10]
// With filter
[for i in 0..10: if i > 5 { i }]
// Result: [6, 7, 8, 9]
// With transformation
[for item in items: item.name]

Form 2: Block Body (For Resources)

var environments = ["dev", "staging", "prod"]
[for env in environments]
resource S3.Bucket bucket {
    name         = "photos-${env}"
}

Form 3: Standalone For Loop

for i in 0..10 {
    var doubled = i * 2
}

Comprehension with Conditionals

// Inline if
[for i in 0..10: if (i % 2 == 0) i]
// Result: [0, 2, 4, 6, 8]
// If-else
[for i in 0..10: if i > 5 { i * 2 } else { i }]
// Result: [0, 1, 2, 3, 4, 5, 12, 14, 16, 18]

Nested Comprehensions

var matrix = [
    [for j in 0..3: i * 3 + j]
    for i in 0..3
]
// Result: [[0,1,2], [3,4,5], [6,7,8]]

Creating Multiple Resources

Using @count Decorator

@count(3)
resource EC2.Instance server {
    name = "server-${count}"
}
// Creates: server-0, server-1, server-2

Using For Loops

var zones            = ["us-east-1a", "us-east-1b", "us-east-1c"]
[for zone in zones]
resource EC2.Instance server {
    name             = "server-${zone}"
    availabilityZone = zone
}

Conditional Resource Creation

var createBackup = true
if createBackup {
    resource S3.Bucket backup {
        name     = "backup-bucket"
    }
}

Control Flow in Components

component WebApp {
    input number replicas     = 1
    input boolean enableCache = false
    @count(replicas)
    resource EC2.Instance server {
        name                  = "server-${count}"
    }
    // Conditional resource
    if enableCache {
        resource ElastiCache.Cluster cache {
            name              = "app-cache"
        }
    }
}

Best Practices

Use Braces Consistently

Always use braces, even for single statements:

// Recommended
if x > 5 {
    doSomething()
}
// Not allowed anyway
if x > 5 doSomething()  // ERROR

Prefer For Loops for Resources

When creating multiple similar resources:

// Good - explicit iteration
for env in ["dev", "staging", "prod"]
resource S3.Bucket bucket {
    name = "data-${env}"
}
// Also good - count decorator
@count(3)
resource EC2.Instance server {
    name = "server-${count}"
}

Use Comprehensions for Data Transformation

var servers   = [
    { name: "web", port: 80 },
    { name: "api", port: 8080 },
    { name: "db", port: 5432 }
]
// Extract names
var names     = [for s in servers: s.name]
// Result: ["web", "api", "db"]
// Filter by port
var highPorts = [for s in servers: if s.port > 1000 { s.name }]
// Result: ["api", "db"]

Next: Learn about Strings - string types and interpolation.