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#
#
# Nim's Runtime Library
# (c) Copyright 2020 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## 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.
import std/[macros, private / underscored_calls]
macro with*(arg: typed; calls: varargs[untyped]): untyped =
## This macro provides `chaining`:idx: 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!
runnableExamples:
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
result = newNimNode(nnkStmtList, arg)
underscoredCalls(result, calls, arg)
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