The tour, 4 of 11

Functions

Parameters, defaults and named arguments, tuples, lambdas, and closures.

A Function’s parameters and result have their types written. One without a result type gives nothing, and one that’s a single expression can be written after =>.

Import std.core

Function Add(a: Int, b: Int): Int
    Return a + b
End Function

Function Square(x: Float): Float => x * x

Function Greet(name: String)
    Print("Hello, {name}")
End Function

Print(Add(2, 3), Square(1.5))
Greet("Ada")

Output

5 2.25
Hello, Ada

Functions are seen anywhere in their file, above or below the code that calls them.

Defaults and named arguments

Import std.core

Function Spawn(name: String, hp: Int = 100, boss: Bool = False): String
    Return "{name} ({hp} hp{boss ? ", boss" : ""})"
End Function

Print(Spawn("grunt"))
Print(Spawn("ogre", 400))
Print(Spawn("king", boss: True))

Output

grunt (100 hp)
ogre (400 hp)
king (100 hp, boss)

Tuples

A Function gives several values as a tuple, which a Local takes apart.

Import std.core

Function MinMax(values: Int[]): (Int, Int)
    Local low = values[0]
    Local high = values[0]
    For v In values
        If v < low Then low = v
        If v > high Then high = v
    End For
    Return (low, high)
End Function

Local low, high = MinMax([4, 9, 1, 7])
Print("from {low} to {high}")

Output

from 1 to 9

Lambdas and closures

A Function is a value too, of a type like Func(Int): Int. A lambda can use the variables around it, and keeps them as long as it lives.

Import std.core

Function MakeCounter(): Func(): Int
    Local count = 0
    Return Function()
        count += 1
        Return count
    End Function
End Function

Local twice = Function(x: Int) => x * 2
Print(twice(21))

Local next = MakeCounter()
next()
next()
Print(next())

Output

42
3

A ByRef parameter changes the caller’s variable, and the call says so too: Swap(ByRef a, ByRef b). Next: arrays and Maps.

Next: Arrays and Maps

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