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Provides default overloads and utilities for macros of definitions.

Examples

# regular definition
a := b

# definition block
def: a = b
def:
  a = b
  c = d

# scoped definition block
def:
  a = b
do:
  use a

# mutable variable definition
@a := b
a := var b
def: @a = b

# assignment to existing variable
^a := b

# aliasing
a as b := c
a := b := c

# checks (for matching)
== 1 := 2 # raises exception
1 := 2 # same, literals inferred to be equality checks
(== ok, res) := (ok, 1)
(in [1, 2, 3]) := 2
(is float) := 2.0
!= 1 := 2
(notin [1, 2, 3]) := 4
(isnot int) := 2.0

# collection unpacking (works for anything if it can be indexed with integers):
(a, b, c) := d
(a) := d # single parens does not unpack, equivalent to a := b
(a,) := d # equivalent to a := b[0]

# default syntax supports brackets instead of parens:
[a, b, c] := d
[a] := d # equivalent to a := d[0]

# collection spreading (works if you can do d[i], d[i..^j] and d[^i]):
(a, *b, c) := d
(a, ..b, c) := d
(a, ...b, c) := d

# nesting (applies to everything)
(a, b) as @c := d # => let temp = d; let a = temp[0]; let b = temp[1]; var c = temp

# empty tuple unpacking, discards right hand side:
() := a

# named unpacking, works on anything (prop1 and prop2 must be identifiers):
(prop1: a, prop2: b) := c

# unpacking by given index:
(0..4: hello, 6..^1: world) := "hello world"
import json
("name": name, "age": age) := %*{"name": "John", "age": 30}

# indexing by identifier if brackets used instead of parens (for enum indexed arrays):
[index1: a, index2: b] := c

# conversion to type:
a of int := 4.0
type Obj = ref object of RootObj
type Obj2 = ref object of Obj
let x: Obj = Obj2()
y of Obj2 := x

# type annotation (must be directly tied to identifiers):
a is uint8 := 4

# option unpacking, only custom type implementation that comes with the library:
Some(a) := b
some(a) := b

Custom definitions

A large and important feature in this package is that you can overload definitions for custom types by importing assigns/impl. The assign macro in this module is overloadable, and the openAssign template creates a NimNode that calls a forced open symbol of assign with the AST of the left hand side, AST of the right hand side, and the flag of whether or not it is a let, var, or mutating assignment. You can use the implementAssign and implementAssignExported templates as a shorthand for declaring these overloads.