npeg_trace.nim

  when npegTrace:
    proc doTrace[sType](
      msg   : string,
      opname: string,
      iname : string,
      ip    : int,
      s     : openArray[sType],
      si    : int,
      ms    : var MatchState,
    ) =
        sleep(500)
        echo align(if ip >= 0: $ip else: "", 3) &
          "|" & align($(peek(ms.precStack)), 3) &
          "|" & align($`si`, 3) &
          "|" & alignLeft(dumpSubject(s, `si`, 24), 24) &
          "|" & alignLeft(iname, 15) &
          "|" & alignLeft(opname & " " & msg, 40) &
          "|" & repeat("*", ms.backStack.top)
    result = quote:
      template trace(`ms`: var MatchState, iname, opname: string, `s`: openArray[`sType`], msg = "") =
        doTrace(msg, opname, iname, `ip`, `s`, `si`, `ms`)