By Reuters Staff 2 Min Read May 18 (Reuters) - Canada’s main stock index was flat on Tuesday as losses in energy firms offset gains in mining companies, while investors looked ahead to inflation data due on Wednesday for cues about economic recovery. * The energy sector dropped 0.2% as U.S. crude prices were down 0.2% a barrel, while Brent crude lost 0.1%. * The materials sector, which includes precious and base metals miners and fertilizer companies, gained 0.4% as gold futures rose 0.2% to $1,870.5 an ounce. * At 9:47 a.m. ET (1347 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 8.47 points, or 0.04%, at 19,466.18.