monoid.nim

import sequtils

proc append[T](a, b: T): T = a + b
proc append[T: seq](a, b: T): T = concat(a, b)

proc zero[S](t: typedesc[seq]): S = @[]
proc zero[S](t: typedesc[int]): S = 0
proc zero[S](t: typedesc[float]): S = 0.0

proc multiply[T: typedesc](t: T, times: int): T =
  if times <= 0:
    zero(T)
  else:
    for i in 1..times:
      result = append(result, t)

echo(multiply(3, 3))
echo(multiply(@[1, 2, 3], 3))