Introduction Functions

Collections

Lists

We can make a list with the List function. 0

import stdlib.collections.list.*;
exported func main() {
l = List<int>();
l.add(1);
l.add(3);
l.add(7);
foreach x in l {
println(x);
}
}

1 3 7

Another way to write the above:

import stdlib.collections.list.*;
exported func main() {
l = List<int>().add(1).add(3).add(7);
foreach x in l {
println(x);
}
}

1 3 7

Loops

As seen above, we can loop with the foreach statement.

We can loop over many things: lists, arrays, even integer ranges:

import stdlib.*;
import stdlib.math.*;

exported func main() {
foreach x in range(0, 3) {
println(x);
}
}

0 1 2

When iterating over collections, we can also get the index of the current iteration with the entries() function.

import stdlib.*;
import stdlib.collections.list.*;

exported func main() {
l = List<int>().add(1).add(3).add(7);
foreach [i, x] in l.entries() {
println(i + ": " + x);
}
}

0: 1 1: 3 2: 7

We can also do the above with a while loop:

import stdlib.*;
import stdlib.collections.list.*;

exported func main() {
l = List<int>().add(1).add(3).add(7);
i = 0;
while i < l.len() {
x = l.get(i);
println(i + ": " + x);
set i = i + 1;
}
}

0: 1 1: 3 2: 7

To interrupt a loop early and skip to the code after it, use the break keyword:

import stdlib.*;
import stdlib.collections.list.*;

exported func main() {
l = List<int>().add(1).add(3).add(7);
foreach [i, x] in l.entries() {
println(i + ": " + x);
if i == 1 {
break;
}
}
}

0: 1 1: 3

Side Notes

(interesting tangential thoughts)

Notes [–] Notes [+] 0

0

Vale's lists are like C#'s List, Java's ArrayList or C++'s vector; it's an array list, not a linked list.

Arrays

One doesn't often need arrays because Lists are easier, but arrays can sometimes be faster.

There are two kinds of arrays in Vale:

Static-sized arrays, where the size is known at compile time.
Runtime-sized arrays, where the size is known only at run time.

Static-sized Arrays

If you know size is known at compile-time, then you can use a static-sized array.

[#5]int is a static-sized array of 5 integers.

There are three ways to make one:

Specify the values: [#5][0, 2, 4, 6, 8].

The size is optional, [#][0, 2, 4, 6, 8] is also valid. Specify a "fill function": [#5](i => i * 2), see example.

To access the element at index 3 in an array arr, we use arr[3]. Note that the first element is index 0, so index 3 is the fourth element.

import stdlib.*;

exported func main() {
arr = [#5](i => i * 2);
foreach i in range(0, 5) {
println(arr[i]);
}
}

0 2 4 6 8

Runtime-sized Arrays

A runtime-sized array is like a List, in that its size can change. However, its capacity cannot change. 1

[]int is a runtime-sized array of integers.

To make a new runtime-sized array, we use the []type(capacity) syntax:

[] means we're making a runtime-sized array.
The type parameter is the type of the elements.
The capacity parameter is how many elements this array can hold.

To access the element at index 3 in an array arr, we use arr[3]. Note that the first element is index 0, so index 3 is the fourth element.

import stdlib.*;
import stdlib.math.*;
import stdlib.stdin.*;

exported func main() {
n = stdinReadInt(); 2
arr = []int(n); 3
foreach i in range(0, n) {
push(&arr, i * 5);
}
foreach i in range(0, n) {
println(arr[i]);
}
}

3

0 5 10

We can also populate it with a function, with the []type(capacity, func) syntax.

The func will be called for each element.

In this example, x => x * 5 is the function that will populate the array.

import stdlib.*;
import stdlib.math.*;
import stdlib.stdin.*;

exported func main() {
n = stdinReadInt();
arr = [](n, x => x * 5);
foreach i in range(0, n) {
println(arr[i]);
}
}

3

0 5 10

Notes [–] Notes [+] 1 2 3

1

This may seem unusual coming from other languages. This decision helps us not need default values for our elements.

2

stdinReadInt reads an integer from the user's keyboard. In this example, the user is entering 3.

stdinReadInt is temporary and experimental, expect the stdin/stdout API to change soon.

3

The type of arr here is []int.

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