alias declarations #7090
Description
More or less what you have in C, with the 'define' preprocessor directive, but in a type-safe manner.
This may be possible in eg a macro or template that could be added to stdlib.
Basically what D describes over here:
https://dlang.org/spec/declaration.html#alias
Meaning that eg, code like this (from Platformer tut):
proc handleInput(game: Game) =
var event = defaultEvent
while pollEvent(event):
case event.kind
of QuitEvent:
game.inputs[Input.quit] = true
of KeyDown:
game.inputs[event.key.keysym.scancode.toInput] = true
of KeyUp:
game.inputs[event.key.keysym.scancode.toInput] = false
else:
discard
Can be expressed as something like this, for instance:
proc handleInput(game: Game) =
alias inputs = game.inputs[event.key.keysym.scancode.toInput]
var event = defaultEvent
while pollEvent(event):
case event.kind
of QuitEvent:
game.inputs[Input.quit] = true
of KeyDown:
inputs = true
of KeyUp:
inputs = false
else:
discard
It's possible currently to get a lot of these kinds of effects by making use of some combination of const or template, or inlined function, but it's a bit untidy or verbose.
Here's one basic example of it from the Nim forum:
https://forum.nim-lang.org/t/1515
It's also something that Ada lets you do with its "rename" syntax, eg:
http://www.adaic.org/resources/add_content/docs/95style/html/sec_5/5-7-2.html
https://en.wikibooks.org/wiki/Ada_Programming/Basic#"Hello,_world!"_with_renames