And i would like to share a macro for same pattern:
import macros
import tables
macro ctor*(none: untyped): auto =
let args = callsite()
if args[1].kind != nnkProcDef:
error("`ctor` pragma is used only with procedures.")
var prc = args[1]
if $(if prc[0].kind == nnkPostfix: prc[0][1] else: prc[0]) notin ["new",
"init"]:
error("Constructor must be named `new` if it returns a ref type or
`init` if it returns a value type.")
var params = prc[3]
var resultType = params[0]
var typeParam = newNimNode(nnkIdentDefs).add(
newIdentNode("_"),
newNimNode(nnkBracketExpr).add(
newIdentNode("typedesc"),
resultType.copyNimTree()
),
newNimNode(nnkEmpty)
)
params.insert(1, typeParam)
result = newStmtList(prc)
proc init*[A, B](initial_size=64): Table[A, B] {.ctor, inline.} =
init_table[A, B](initial_size)
discard Table[int, int].init()
You delcare init or new proc with ctor pragma and it inserts first typedesc
parameter automatically based on return type of the proc. Works with templates
and everything.
