Replacement for negative indices

neg_ind.nim

var s = "abcdef"
echo s[2 .. -3] # I suggest to remove this
# cd

proc `^`(x: int): int = assert false

template ex{`[]`(s, `..`(a, `^`(b)))}(s: expr{noSideEffect}, a, b: int): expr =
  s[a .. s.len+b]

echo s[2 .. ^ -3] # Easy fix in code
# cd


# Or even this

proc `^-`(x: int): int = assert false

template ex{`[]`(s, `..`(a, `^-`(b)))}(s: expr{noSideEffect}, a, b: int): expr =
  s[a .. s.len-b]


echo s[2 .. ^-3]
# cd

echo(@[1,2,3,4,5,6][2 .. ^-3])
# @[3, 4]