64 lines
1.7 KiB
Markdown
64 lines
1.7 KiB
Markdown
---
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title: Arrays
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---
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# Arrays
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The arrays in Nim are like classic C arrays, their size is specified at compile-time and cannot given or changed at runtime.
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``` nimrod
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type
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ThreeStringAddress = array[3, string]
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let names: ThreeStringAddress = ["Jasmine", "Ktisztina", "Kristof"]
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let addresses: ThreeStringAddress = ["101 Betburweg", "66 Bellion Drive", "194 Laarderweg"]
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```
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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.
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``` nimrod
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proc zip[I, T](a, b: array[I, T]):
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array[I, tuple[a, b: T]] =
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for i in low(a)..high(a):
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result[i] = (a[i], b[i])
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let nameAndAddresses = names.zip(addresses)
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```
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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:
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``` nimrod
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type
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PartsOfSpeech {.pure.} = enum
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Pronoun, Verb, Article, Adjective, Noun, Adverb
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let partOfSpeechExamples: array[PartsOfSpeech, string] = [
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"he", "reads", "the", "green", "book", "slowly"
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]
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```
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``` nimrod
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type
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Matrix[W, H: static[int]] =
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array[1..W, array[1..H, int]]
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let mat1: Matrix[2, 2] = [[1, 0],
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[0, 1]]
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let mat2: Matrix[2, 2] = [[0, 1],
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[1, 0]]
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proc `+`[W, H](a, b: Matrix[W, H]):
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Matrix[W, H] =
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for i in 1..high(a):
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for j in 1..high(a[0]):
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result[i][j] = a[i][j] + b[i][j]
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# See `$` from the procs section
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echo mat1 + mat2
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```
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``` console
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$ nim c -r matrix.nim
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1, 1,
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1, 1,
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```
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