system/iterators

Default iterators for some Nim types.

Iterators

iterator fieldPairs[S: tuple | object; T: tuple | object](x: S; y: T): tuple[
    key: string, a, b: RootObj] {.magic: "FieldPairs", noSideEffect, ...raises: [],
                                  tags: [], forbids: [].}

Iterates over every field of x and y.

Warning: This really transforms the 'for' and unrolls the loop. The current implementation also has a bug that affects symbol binding in the loop body.

Example:

type Foo = object
  x1: int
  x2: string
var a1 = Foo(x1: 12, x2: "abc")
var a2: Foo
for name, v1, v2 in fieldPairs(a1, a2):
  when name == "x2": v2 = v1
doAssert a2 == Foo(x1: 0, x2: "abc")

Source Edit

iterator fieldPairs[T: tuple | object](x: T): tuple[key: string, val: RootObj] {.
    magic: "FieldPairs", noSideEffect, ...raises: [], tags: [], forbids: [].}

Iterates over every field of x returning their name and value.

When you iterate over objects with different field types you have to use the compile time when instead of a runtime if to select the code you want to run for each type. To perform the comparison use the is operator. Another way to do the same without when is to leave the task of picking the appropriate code to a secondary proc which you overload for each field type and pass the value to.

Warning: This really transforms the 'for' and unrolls the loop. The current implementation also has a bug that affects symbol binding in the loop body.

Example:

type
  Custom = object
    foo: string
    bar: bool
proc `$`(x: Custom): string =
  result = "Custom:"
  for name, value in x.fieldPairs:
    when value is bool:
      result.add("\n\t" & name & " is " & $value)
    else:
      result.add("\n\t" & name & " '" & value & "'")

Source Edit

iterator fields[S: tuple | object; T: tuple | object](x: S; y: T): tuple[
    key: string, val: RootObj] {.magic: "Fields", noSideEffect, ...raises: [],
                                 tags: [], forbids: [].}

Iterates over every field of x and y.

Warning: This really transforms the 'for' and unrolls the loop. The current implementation also has a bug that affects symbol binding in the loop body.

Example:

var t1 = (1, "foo")
var t2 = default(typeof(t1))
for v1, v2 in fields(t1, t2): v2 = v1
doAssert t1 == t2

Source Edit

iterator fields[T: tuple | object](x: T): RootObj {.magic: "Fields",
    noSideEffect, ...raises: [], tags: [], forbids: [].}

Iterates over every field of x.

Warning: This really transforms the 'for' and unrolls the loop. The current implementation also has a bug that affects symbol binding in the loop body.

Example:

var t = (1, "foo")
for v in fields(t): v = default(typeof(v))
doAssert t == (0, "")

Source Edit

iterator items(a: cstring): char {.inline, ...raises: [], tags: [], forbids: [].}

Iterates over each item of a.

Example:

from std/sequtils import toSeq
assert toSeq("abc\0def".cstring) == @['a', 'b', 'c']
assert toSeq("abc".cstring) == @['a', 'b', 'c']

Source Edit

iterator items(a: string): char {.inline, ...raises: [], tags: [], forbids: [].}

Iterates over each item of a. Source Edit

iterator items[IX, T](a: array[IX, T]): T {.inline.}

Iterates over each item of a. Source Edit

iterator items[T: char](a: openArray[T]): T {.inline.}

Iterates over each item of a. Source Edit

iterator items[T: enum and Ordinal](E: typedesc[T]): T

Iterates over the values of E. See also enumutils.items for enums with holes.

Example:

type Goo = enum g0 = 2, g1, g2
from std/sequtils import toSeq
assert Goo.toSeq == [g0, g1, g2]

Source Edit

iterator items[T: not char](a: openArray[T]): lent2 T {.inline.}

Iterates over each item of a. Source Edit

iterator items[T: Ordinal](s: Slice[T]): T

Iterates over the slice s, yielding each value between s.a and s.b (inclusively). Source Edit

iterator items[T](a: seq[T]): lent2 T {.inline.}

Iterates over each item of a. Source Edit

iterator items[T](a: set[T]): T {.inline.}

Iterates over each element of a. items iterates only over the elements that are really in the set (and not over the ones the set is able to hold). Source Edit

iterator mitems(a: var cstring): var char {.inline, ...raises: [], tags: [],
    forbids: [].}

Iterates over each item of a so that you can modify the yielded value.

Example:

from std/sugar import collect
var a = "abc\0def"
prepareMutation(a)
var b = a.cstring
let s = collect:
  for bi in mitems(b):
    if bi == 'b': bi = 'B'
    bi
assert s == @['a', 'B', 'c']
assert b == "aBc"
assert a == "aBc\0def"

Source Edit

iterator mitems(a: var string): var char {.inline, ...raises: [], tags: [],
    forbids: [].}

Iterates over each item of a so that you can modify the yielded value. Source Edit

iterator mitems[IX, T](a: var array[IX, T]): var T {.inline.}

Iterates over each item of a so that you can modify the yielded value. Source Edit

iterator mitems[T](a: var openArray[T]): var T {.inline.}

Iterates over each item of a so that you can modify the yielded value. Source Edit

iterator mitems[T](a: var seq[T]): var T {.inline.}

Iterates over each item of a so that you can modify the yielded value. Source Edit

iterator mpairs(a: var cstring): tuple[key: int, val: var char] {.inline,
    ...raises: [], tags: [], forbids: [].}

Iterates over each item of a. Yields (index, a[index]) pairs. a[index] can be modified. Source Edit

iterator mpairs(a: var string): tuple[key: int, val: var char] {.inline,
    ...raises: [], tags: [], forbids: [].}

Iterates over each item of a. Yields (index, a[index]) pairs. a[index] can be modified. Source Edit

iterator mpairs[IX, T](a: var array[IX, T]): tuple[key: IX, val: var T] {.inline.}

Iterates over each item of a. Yields (index, a[index]) pairs. a[index] can be modified. Source Edit

iterator mpairs[T](a: var openArray[T]): tuple[key: int, val: var T] {.inline.}

Iterates over each item of a. Yields (index, a[index]) pairs. a[index] can be modified. Source Edit

iterator mpairs[T](a: var seq[T]): tuple[key: int, val: var T] {.inline.}

Iterates over each item of a. Yields (index, a[index]) pairs. a[index] can be modified. Source Edit

iterator pairs(a: cstring): tuple[key: int, val: char] {.inline, ...raises: [],
    tags: [], forbids: [].}

Iterates over each item of a. Yields (index, a[index]) pairs. Source Edit

iterator pairs(a: string): tuple[key: int, val: char] {.inline, ...raises: [],
    tags: [], forbids: [].}

Iterates over each item of a. Yields (index, a[index]) pairs. Source Edit

iterator pairs[IX, T](a: array[IX, T]): tuple[key: IX, val: T] {.inline.}

Iterates over each item of a. Yields (index, a[index]) pairs. Source Edit

iterator pairs[T](a: openArray[T]): tuple[key: int, val: T] {.inline.}

Iterates over each item of a. Yields (index, a[index]) pairs. Source Edit

iterator pairs[T](a: seq[T]): tuple[key: int, val: T] {.inline.}

Iterates over each item of a. Yields (index, a[index]) pairs. Source Edit