Level 18. Building Strings

Sometimes you want to build a message from pieces. Hica gives you two ways.

Gluing strings with +

The + operator works on strings too. It stitches them together:

fun shout(word) => word + "!"

fun main() {
  println(shout("wow"))
}

String interpolation with {}

Even easier: put {expr} right inside a string, and Hica fills in the value:

fun greet(name) => "hello, {name}!"

fun main() {
  println(greet("world"))
}

Numbers and booleans are converted automatically:

fun main() {
  let apples = 5
  println("{apples} apples")
}

You can even put expressions inside the braces:

fun main() {
  let a = 3
  let b = 4
  println("{a} + {b} = {a + b}")
}

Think of {} as little windows into your code. Whatever you put inside gets turned into text and dropped into the string.

🎯 Try it: Write a function introduce(name, age) that returns "my name is ___ and I am ___ years old".

String tools

Hica comes with built-in tools for working with strings: no imports needed:

fun main() {
  let msg = "  Hello, World!  "

  // Trimming — remove extra spaces
  println(trim(msg))           // "Hello, World!"

  // Searching
  println(contains(msg, "World"))    // true
  println(starts_with(trim(msg), "Hello"))  // true

  // Changing case
  println(to_upper("hello"))  // "HELLO"
  println(to_lower("HELLO"))  // "hello"

  // Splitting and joining
  println(split("a,b,c", ","))        // ["a", "b", "c"]
  println(join(["a", "b", "c"], "-")) // "a-b-c"

  // How long is it?
  println(str_length("hello"))  // 5
}

Think of these like tools in a toolbox:

🎯 Try it: Use split to break "red,green,blue" into a list, then join it back with " and ".

Special characters (escape sequences)

What if you want to put a double-quote inside a string? You can’t just write "She said "hi"". Hica would think the string ends at the second ".

The trick: put a backslash \ before the special character. The backslash says “the next character is literal, not magic”:

fun main() {
  println("She said \"hi\"")   // She said "hi"
  println("one\\two")          // one\two  (literal backslash)
}

There are also shortcuts for invisible characters:

fun main() {
  println("line one\nline two")  // prints on two lines!
  println("name\tage")
  println("Ada\t12")
}

Escapes work inside interpolated strings too:

fun main() {
  let name = "world"
  println("hello, {name}!\ngoodbye!")
}

🎯 Try it: Print a tiny two-line poem using \n to separate the lines.

Peeking inside strings (indexing and slicing)

You can grab individual characters or pieces of a string using square brackets , just like picking cards out of a deck:

fun main() {
  let s = "hello"
  println(s[0])      // 'h' — the first character
  println(s[1])      // 'e' — the second character
  println(s[-1])     // 'o' — the last character!
}

Negative numbers count from the end: -1 is the last character, -2 is the second-to-last, and so on.

You can also grab a slice: a piece of the string:

fun main() {
  let s = "hello"
  println(s[1:4])    // "ell" — from position 1 up to (not including) 4
  println(s[:3])     // "hel" — the first 3 characters
  println(s[3:])     // "lo"  — from position 3 to the end
}

Think of it like a ruler laid along the string: the numbers mark the gaps between characters, and you pick the piece between two marks.

🎯 Try it: Given let word = "abcdef", what is word[2:5]? What about word[-2]?