You can do it a bit shorter and easier in Nim as well:

    import macros, strutils
    
    macro abcProcs(n: varargs[expr]): stmt =
      result = newStmtList()
      for c in n.children:
        result.add parseStmt("proc $1 = echo \"$1\"" % $c)
    
    abcProcs("A","B","C")
    
    proc execute(order: openarray[int], callbacks: openarray[proc]) =
      for i in order:
        callbacks[i]()
    
    execute([0,0,1,2,1,2], [A,B,C])