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Cartesian product of two or more lists: Difference between revisions
Cartesian product of two or more lists (view source)
Revision as of 21:55, 30 October 2020
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ReadChar
END CartesianProduct.</lang>
=={{header|Nim}}==
To compute the product of two lists (Nim arrays or sequences), we use an iterator. Obtaining a sequence from an iterator is easily done using "toSeq" from the module “sequtils” of the standard library.
The procedure allows to mix sequences of different types, for instance integers and characters.
In order to display the result using mathematical formalism, we have created a special procedure “$$” for the sequences and have overloaded the procedure “$” for tuples.
<lang Nim>iterator product[T1, T2](a: openArray[T1]; b: openArray[T2]): tuple[a: T1, b: T2] =
# Yield the element of the cartesian product of "a" and "b".
# Yield tuples rather than arrays as it allows T1 and T2 to be different.
for x in a:
for y in b:
yield (x, y)
#———————————————————————————————————————————————————————————————————————————————————————————————————
when isMainModule:
from seqUtils import toSeq
import strformat
from strutils import addSep
#-------------------------------------------------------------------------------------------------
proc `$`[T1, T2](t: tuple[a: T1, b: T2]): string =
## Overloading of `$` to display a tuple without the field names.
&"({t.a}, {t.b})"
proc `$$`[T](s: seq[T]): string =
## New operator to display a sequence using mathematical set notation.
result = "{"
for item in s:
result.addSep(", ", 1)
result.add($item)
result.add('}')
#-------------------------------------------------------------------------------------------------
const Empty = newSeq[int]() # Empty list of "int".
for (a, b) in [(@[1, 2], @[3, 4]),
(@[3, 4], @[1, 2]),
(@[1, 2], Empty ),
( Empty, @[1, 2])]:
echo &"{$$a} x {$$b} = {$$toSeq(product(a, b))}"</lang>
{{out}}
<pre>1, 2} x {3, 4} = {(1, 3), (1, 4), (2, 3), (2, 4)}
{3, 4} x {1, 2} = {(3, 1), (3, 2), (4, 1), (4, 2)}
{1, 2} x {} = {}
{} x {1, 2} = {}</lang>
=={{header|OCaml}}==
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