https://github.com/zevv/with

with macro for Nim
https://github.com/zevv/with

Last synced: about 2 months ago
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with macro for Nim

• Host: GitHub
• URL: https://github.com/zevv/with
• Owner: zevv
• Created: 2019-01-27T19:58:19.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2023-01-29T14:41:09.000Z (over 1 year ago)
• Last Synced: 2024-05-18T03:34:22.303Z (4 months ago)
• Language: Nim
• Size: 448 KB
• Stars: 85
• Watchers: 4
• Forks: 5
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

• awesome-nim - with - The `with` macro for Nim. (Language Features / Macros)

README

        

> _`with` is fun, but as its own project it should have a splash image like "Inspired by a forbidden(TM) JavaScript feature!"_

> -jrfondren

`with` is a simple macro to replace the deprecated ``{.with.}`` pragma in Nim.

This macro allow you to access fields of an object or tuple without having to

repeatedly type its name. It works by creating tiny templates with the same

name as the field that expand to access to the field in the object.

Example:

```nim

type Foo = ref object

  first: int

  second: string

  third: float

var foo = Foo(first: 1, second: "two", third: 3.0)

with foo:

  echo first

  if true:

    third = float(first)

  echo second

```

``with`` also works with named tuples:

```nim

var foo = (first: 1, second: "two")

with foo:

  first = 3

  second = "six"

```

Fields from the object can be shadowed by new declarations in the scope where

the new declaration is made. The object field can still be accessed by using its

full dot-expression notation:

```nim

var foo = (first: 1, second: "two")

with foo:

  assert first == 1

  if true:

    let first = "dragons"

    assert first == "dragons" 

    assert foo.first == 1

  assert first == 1

  assert foo.first == 1

```

For the brave, ``with`` blocks can be nested, or multiple objects can be passed

in a tuple constructor. Make sure that field names are unique in the nested

objects:

```nim

var foo = (first: 1, second: "two")

var bar = (alpha: 42)

with foo:

  with bar:

    first = alpha

with (foo,bar):

  first = alpha

```