Reference

How syntax works

Syntax is the small stuff that holds a program together — brackets, keywords, one symbol versus another. Most first mistakes are syntax, not ideas. The lab lets you take the training wheels off one at a time: tap tiles into the blanks, then type with a palette, then write it all yourself. Here are the syntax rules it drills. Open the syntax lab →

print( … ) uses round brackets

A function call puts its value inside round ( ) brackets — never square [ ] or curly { }.
```
print(6 + 4)
```
prints 10
One = stores · two == asks

A single = puts a new value into a box. Two == only ASKS "are these equal?" and stores nothing.
```
var n = 3
n = n + 5
print(n)
```
prints 8
if uses curly braces { }

The body that runs "if it is true" goes inside curly braces. Swift has no "then" and no "end".
```
if 7 > 5 {
  print("big")
}
```
prints big
..< stops before · ... includes

0 ..< 3 is 0, 1, 2 (not 3). 0 ... 3 would add the 3. Pick the one that gives the count you want.
```
for i in 0..<3 {
  print(i)
}
```
prints 0 ⏎ 1 ⏎ 2
return hands a value back

Inside a function, return sends the answer back to whoever called it. print would only show it.
```
func double(n: Int) -> Int {
  return n * 2
}
print(double(5))
```
prints 10
.append and .count are the list words

A Swift list grows with .append(x) and is measured with .count — not add / push / length / size.
```
var xs = [1]
xs.append(2)
print(xs.count)
```
prints 2
&& needs both · || needs one

&& (AND) is true only when BOTH sides are true; || (OR) is true when either is. Swift uses the symbols.
```
if true && false {
  print("both")
} else {
  print("not both")
}
```
prints not both
Whole numbers divide with /, but // is a comment

17 / 5 is 3 (the remainder is dropped). Watch out: // does not divide — it starts a comment!
```
print(17 / 5)
```
prints 3

Every program in SyntaxForge is written in a teaching subset of the Swift language — the same rules real programmers use, kept small so you can build it by hand. Build one →