Types

Board = array[length, Column]: Board data structure
Column = object free: uint content: array[length, string]: Column data structure

Lets

proc add(column: uint; player: string; board: var Board): bool {....raises: [], tags: [].}: add player to the column if possible
proc checkWinner(board: Board; round: uint): bool {....raises: [IOError, ValueError, RegexInternalError, InvalidUnicodeError, KeyError, SyntaxError, StudyError], tags: [ExecIOEffect, WriteIOEffect].}: check for winner (horizontal, vertical, diagonal)
proc getCol(p: string): uint {....raises: [IOError], tags: [ReadIOEffect, WriteIOEffect].}: ask user for a column between 1 and 7
proc initBoard(): Board {....raises: [], tags: [].}: set all the case of the board to a '.'
proc show(b: Board) {....raises: [IOError], tags: [ExecIOEffect, WriteIOEffect].}: show the formatted board to the screen
proc to_string(b: Board): string {....raises: [], tags: [].}: convert the board to a one line string