iterator - 在 Nim 中将迭代器作为参数传递失败 "attempting to call undeclared routine"

Question

我正在尝试通过编写一个我已经用其他语言实现的生物信息学工具来学习 Nim。

我有以下版本，显然可以正确编译和运行:

from strutils import join
from sequtils import zip

type
  Nucleotides = distinct string
  Qualities = distinct string
  #Nucleotides = string
  #Qualities = string
  Fastq = tuple
    name: string
    nucls: Nucleotides
    quals: Qualities

# proc `==` (ns, ms: Nucleotides): bool =
#   string(ns) == string(ms)
# https://nim-by-example.github.io/types/distinct/
proc `==` (ns, ms: Nucleotides): bool {.borrow.}

proc makeFastq(name, nucls, quals: string): Fastq =
  result = (name: name, nucls: nucls.Nucleotides, quals: quals.Qualities)

proc bestQuals(quals1, quals2: string): string =
  let N = min(quals1.len, quals2.len)
  result = newStringOfCap(N)
  for pair in zip(quals1, quals2):
    result.add(chr(max(ord(pair.a), ord(pair.b))))

proc bestQuals(quals1, quals2: Qualities): Qualities =
  result = bestQuals(string(quals1), string(quals2)).Qualities

proc fuseFastq(rec1, rec2: Fastq): Fastq =
  result = (name: rec1.name, nucls: rec1.nucls, quals: bestQuals(rec1.quals, rec2.quals))

proc `$` (record: Fastq): string =
  result = join([
    record.name,
    string(record.nucls),
    "+",
    string(record.quals)], "\n")

iterator parseFastqs(input: File): Fastq =
  var
    nameLine: string
    nucLine: string
    quaLine: string
  while not input.endOfFile:
    nameLine = input.readLine()
    nucLine = input.readLine()
    discard input.readLine()
    quaLine = input.readLine()
    yield makeFastq(nameLine, nucLine, quaLine)

proc deduplicate() =
  var
    record: Fastq
  record = (name: "", nucls: "".Nucleotides, quals: "".Qualities)
  for fastq in parseFastqs(stdin):
    if record.nucls != fastq.nucls:
      if record.name != "":
        echo $record
      record = fastq
    else:
      record = fuseFastq(record, fastq)
      continue
  if record.name != "":
    echo $record

when isMainModule:
  deduplicate()

现在，我想要 deduplicate将生成 Fastq 的“事物”(当前是迭代器)作为参数元组。拥有 when isMainModule 确实看起来更干净部分处理从 stdin 或将来可能的其他内容读取(例如，作为命令行参数传递的文件):

proc deduplicate(inputFqs: <some relevant type>) =
  var
    record: Fastq
  record = (name: "", nucls: "".Nucleotides, quals: "".Qualities)
  for fastq in inputFqs:
    if record.nucls != fastq.nucls:
      if record.name != "":
        echo $record
      record = fastq
    else:
      record = fuseFastq(record, fastq)
      continue
  if record.name != "":
    echo $record

when isMainModule:
  let inputFqs = parseFastqs(stdin)
  deduplicate(inputFqs)

有没有简单有效的方法来做到这一点？

我天真地尝试了以下方法:

proc deduplicate(inputFqs: iterator) =
  var
    record: Fastq
  record = (name: "", nucls: "".Nucleotides, quals: "".Qualities)
  for fastq in inputFqs:
    if record.nucls != fastq.nucls:
      if record.name != "":
        echo $record
      record = fastq
    else:
      record = fuseFastq(record, fastq)
      continue
  if record.name != "":
    echo $record

when isMainModule:
  let inputFqs = parseFastqs(stdin)
  deduplicate(inputFqs)

这会导致以下编译错误: Error: attempting to call undeclared routine: 'parseFastqs' .

我从 manual搜索理解我应该让我的迭代器成为闭包迭代器。所以我开始只是使用 {.closure.}附注:

iterator parseFastqs(input: File): Fastq {.closure.} =

但我一直有同样的错误。

所以我试着更接近地模仿手册中给出的例子:

iterator parseFastqs(input: File): Fastq {.closure.} =
  var
    nameLine: string
    nucLine: string
    quaLine: string
  while not input.endOfFile:
    nameLine = input.readLine()
    nucLine = input.readLine()
    discard input.readLine()
    quaLine = input.readLine()
    yield makeFastq(nameLine, nucLine, quaLine)

proc deduplicate(inputFqs: iterator(): Fastq {.closure.}) =
  var
    record: Fastq
  record = (name: "", nucls: "".Nucleotides, quals: "".Qualities)
  for fastq in inputFqs:
    if record.nucls != fastq.nucls:
      if record.name != "":
        echo $record
      record = fastq
    else:
      record = fuseFastq(record, fastq)
      continue
  if record.name != "":
    echo $record

deduplicate(parseFastqs(stdin))

这导致了类型错误:

Error: type mismatch: got (iterator (): Fastq{.closure.})
but expected one of: 
iterator items[T](a: set[T]): T
iterator items(a: cstring): char
iterator items[T](a: openArray[T]): T
iterator items[IX, T](a: array[IX, T]): T
iterator items(a: string): char
iterator items[T](a: seq[T]): T
iterator items(E: typedesc[enum]): E:type
iterator items[T](s: HSlice[T, T]): T

expression: items(inputFqs)

我究竟做错了什么？

编辑:解决类型问题

看来类型不匹配可以通过改变 for fastq in inputFqs:来解决至 for fastq in inputFqs(): .情况回到 Error: attempting to call undeclared routine: 'parseFastqs' .

对手册中示例的一些修改表明迭代器参数的类型不需要括号。以下编译并正确运行:

iterator count0(): int {.closure.} =
  yield 0

iterator count2(): int {.closure.} =
  var x = 1
  yield x
  inc x
  yield x

proc invoke(iter: iterator) =
  for x in iter(): echo x

invoke(count0)
invoke(count2)

现在我会对 感兴趣括号的含义在原始示例中:

proc invoke(iter: iterator(): int {.closure.}) =

Answer 1

您必须遍历 iterator

for item in myIterator():
  echo repr item

或者你可以把它转换成一个序列

import sequtils
echo toSeq(myIterator())