std/with

Source Edit

This module implements the with macro for easy function chaining. See https://github.com/nim-lang/RFCs/issues/193 and https://github.com/nim-lang/RFCs/issues/192 for details leading to this particular design.

Since: version 1.2.

Imports

macros, underscored_calls

Macros

macro with(arg: typed; calls: varargs[untyped]): untyped

This macro provides chaining of function calls. It does so by patching every call in calls to use arg as the first argument.

Caution: This evaluates arg multiple times!

Example:

var x = "yay"
with x:
  add "abc"
  add "efg"
doAssert x == "yayabcefg"

var a = 44
with a:
  += 4
  -= 5
doAssert a == 43

# Nesting works for object types too!
var foo = (bar: 1, qux: (baz: 2))
with foo:
  bar = 2
  with qux:
    baz = 3
doAssert foo.bar == 2
doAssert foo.qux.baz == 3

Source Edit