⚠️ This guide has not been actively kept up to date since before Nim 1.0. Many things are still the same, but some things have changed.

# Arrays

The arrays in Nim are like classic C arrays, their size is specified at compile-time and cannot be given or changed at runtime.

``````type
let names: ThreeStringAddress = ["Jasmine", "Ktisztina", "Kristof"]

The size of the array is encoded in its type and cannot be accidentally lost. Therefore, a procedure taking an array of variable length must encode the length in its type parameters.

``````proc zip[I, T](a, b: array[I, T]):
array[I, tuple[a, b: T]] =
for i in low(a)..high(a):
result[i] = (a[i], b[i])

Alternate methods of indexing arrays are also allowed, the first type parameter is actually a range (just a value, as above, is syntactic sugar for `0..N-1`). It’s also possible to use ordinal values to index an array, effectively creating a lookup table:

``````type
PartsOfSpeech {.pure.} = enum
let partOfSpeechExamples: array[PartsOfSpeech, string] = [
"he", "reads", "the", "green", "book", "slowly"
]``````
``````type
Matrix[W, H: static[int]] =
array[1..W, array[1..H, int]]

let mat1: Matrix[2, 2] = [[1, 0],
[0, 1]]
let mat2: Matrix[2, 2] = [[0, 1],
[1, 0]]

proc `+`[W, H](a, b: Matrix[W, H]):
Matrix[W, H] =
for i in 1..high(a):
for j in 1..high(a[0]):
result[i][j] = a[i][j] + b[i][j]

# See `\$` from the procs section

echo mat1 + mat2``````
``````\$ nim c -r matrix.nim
1, 1,
1, 1,``````