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#
#
# Nimrod's Runtime Library
# (c) Copyright 2011 Alex Mitchell
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## :Author: Alex Mitchell
##
## This module implements operations for the built-in `seq`:idx: type which
## were inspired by functional programming languages. If you are looking for
## the typical `map` function which applies a function to every element in a
## sequence, it already exists in the `system <system.html>`_ module in both
## mutable and immutable styles.
##
## Also, for functional style programming you may want to pass `anonymous procs
## <manual.html#anonymous-procs>`_ to procs like ``filter`` to reduce typing.
## Anonymous procs can use `the special do notation <manual.html#do-notation>`_
## which is more convenient in certain situations.
##
## **Note**: This interface will change as soon as the compiler supports
## closures and proper coroutines.
when not defined(nimhygiene):
{.pragma: dirty.}
proc concat*[T](seqs: varargs[seq[T]]): seq[T] =
## Takes several sequences' items and returns them inside a new sequence.
##
## Example:
##
## .. code-block:: nimrod
## let
## s1 = @[1, 2, 3]
## s2 = @[4, 5]
## s3 = @[6, 7]
## total = concat(s1, s2, s3)
## assert total == @[1, 2, 3, 4, 5, 6, 7]
var L = 0
for seqitm in items(seqs): inc(L, len(seqitm))
newSeq(result, L)
var i = 0
for s in items(seqs):
for itm in items(s):
result[i] = itm
inc(i)
proc distnct*[T](seq1: seq[T]): seq[T] =
## Returns a new sequence without duplicates.
##
## This proc is `misspelled` on purpose to avoid a clash with the keyword
## ``distinct`` used to `define a derived type incompatible with its base
## type <manual.html#distinct-type>`_. Example:
##
## .. code-block:: nimrod
## let
## dup1 = @[1, 1, 3, 4, 2, 2, 8, 1, 4]
## dup2 = @["a", "a", "c", "d", "d"]
## unique1 = distnct(dup1)
## unique2 = distnct(dup2)
## assert unique1 == @[1, 3, 4, 2, 8]
## assert unique2 == @["a", "c", "d"]
result = @[]
for itm in items(seq1):
if not result.contains(itm): result.add(itm)
proc zip*[S, T](seq1: seq[S], seq2: seq[T]): seq[tuple[a: S, b: T]] =
## Returns a new sequence with a combination of the two input sequences.
##
## For convenience you can access the returned tuples through the named
## fields `a` and `b`. If one sequence is shorter, the remaining items in the
## longer sequence are discarded. Example:
##
## .. code-block:: nimrod
## let
## short = @[1, 2, 3]
## long = @[6, 5, 4, 3, 2, 1]
## words = @["one", "two", "three"]
## zip1 = zip(short, long)
## zip2 = zip(short, words)
## assert zip1 == @[(1, 6), (2, 5), (3, 4)]
## assert zip2 == @[(1, "one"), (2, "two"), (3, "three")]
## assert zip1[2].b == 4
## assert zip2[2].b == "three"
var m = min(seq1.len, seq2.len)
newSeq(result, m)
for i in 0 .. m-1: result[i] = (seq1[i], seq2[i])
iterator filter*[T](seq1: seq[T], pred: proc(item: T): bool {.closure.}): T =
## Iterates through a sequence and yields every item that fulfills the
## predicate.
##
## Example:
##
## .. code-block:: nimrod
## let numbers = @[1, 4, 5, 8, 9, 7, 4]
## for n in filter(numbers, proc (x: int): bool = x mod 2 == 0):
## echo($n)
## # echoes 4, 8, 4 in separate lines
for i in countup(0, len(seq1) -1):
var item = seq1[i]
if pred(item): yield seq1[i]
proc filter*[T](seq1: seq[T], pred: proc(item: T): bool {.closure.}): seq[T] =
## Returns a new sequence with all the items that fulfilled the predicate.
##
## Example:
##
## .. code-block:: nimrod
## let
## colors = @["red", "yellow", "black"]
## f1 = filter(colors, proc(x: string): bool = x.len < 6)
## f2 = filter(colors) do (x: string) -> bool : x.len > 5
## assert f1 == @["red", "black"]
## assert f2 == @["yellow"]
accumulateResult(filter(seq1, pred))
template filterIt*(seq1, pred: expr): expr {.immediate, dirty.} =
## Returns a new sequence with all the items that fulfilled the predicate.
##
## Unlike the `proc` version, the predicate needs to be an expression using
## the ``it`` variable for testing, like: ``filterIt("abcxyz", it == 'x')``.
## Example:
##
## .. code-block:: nimrod
## let
## temperatures = @[-272.15, -2.0, 24.5, 44.31, 99.9, -113.44]
## acceptable = filterIt(temperatures, it < 50 and it > -10)
## assert acceptable == @[-2.0, 24.5, 44.31]
var result {.gensym.}: type(seq1) = @[]
for it in items(seq1):
if pred: result.add(it)
result
template toSeq*(iter: expr): expr {.immediate.} =
## Transforms any iterator into a sequence.
##
## Example:
##
## .. code-block:: nimrod
## let
## numeric = @[1, 2, 3, 4, 5, 6, 7, 8, 9]
## odd_numbers = toSeq(filter(numeric) do (x: int) -> bool:
## if x mod 2 == 1:
## result = true)
## assert odd_numbers == @[1, 3, 5, 7, 9]
##
var result {.gensym.}: seq[type(iter)] = @[]
for x in iter: add(result, x)
result
when isMainModule:
import strutils
proc toStr(x: int): string {.procvar.} = $x
# concat test
let
s1 = @[1, 2, 3]
s2 = @[4, 5]
s3 = @[6, 7]
total = concat(s1, s2, s3)
assert total == @[1, 2, 3, 4, 5, 6, 7]
# duplicates test
let
dup1 = @[1, 1, 3, 4, 2, 2, 8, 1, 4]
dup2 = @["a", "a", "c", "d", "d"]
unique1 = distnct(dup1)
unique2 = distnct(dup2)
assert unique1 == @[1, 3, 4, 2, 8]
assert unique2 == @["a", "c", "d"]
# zip test
let
short = @[1, 2, 3]
long = @[6, 5, 4, 3, 2, 1]
words = @["one", "two", "three"]
zip1 = zip(short, long)
zip2 = zip(short, words)
assert zip1 == @[(1, 6), (2, 5), (3, 4)]
assert zip2 == @[(1, "one"), (2, "two"), (3, "three")]
assert zip1[2].b == 4
assert zip2[2].b == "three"
# filter proc test
let
colors = @["red", "yellow", "black"]
f1 = filter(colors, proc(x: string): bool = x.len < 6)
f2 = filter(colors) do (x: string) -> bool : x.len > 5
assert f1 == @["red", "black"]
assert f2 == @["yellow"]
# filter iterator test
let numbers = @[1, 4, 5, 8, 9, 7, 4]
for n in filter(numbers, proc (x: int): bool = x mod 2 == 0):
echo($n)
# echoes 4, 8, 4 in separate lines
# filterIt test
let
temperatures = @[-272.15, -2.0, 24.5, 44.31, 99.9, -113.44]
acceptable = filterIt(temperatures, it < 50 and it > -10)
assert acceptable == @[-2.0, 24.5, 44.31]
# toSeq test
let
numeric = @[1, 2, 3, 4, 5, 6, 7, 8, 9]
odd_numbers = toSeq(filter(numeric) do (x: int) -> bool:
if x mod 2 == 1:
result = true)
assert odd_numbers == @[1, 3, 5, 7, 9]
echo "Finished doc tests"
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