Comcast, the largest U.S. cable operator, has posted a narrower second-quarter loss and reported solid gains in revenue and cash flow. Wall Street was generally pleased with the figures on Thursday,particularly because the company also raised its forecast for increases in cable subscribers and cash flow for the full year. For the quarter, Comcast reported a net loss of $22 million, comparedwith a net loss of $210 million a year earlier Revenue rose 10.2 percent, to $5.68 billion, after adjusting for the acquisition of AT&T Broadband last November. On the same basis, cash flow rose22.9 percent, to $1.83 billion Comcast said it added 12,100 cable subscribers in the quarter, compared with a loss of 133,300 in the quarter a year earlier. Not only was the turnaround striking, butan increase in subscribers in the quarter is unusual, said Dennis Leibowitz, who runs Act II Partners, a hedge fund that specializes in media companies. The chief executive, Brian Roberts, saidComcast, which had been expecting no growth in subscribers for the full year because it was working to stem losses on the former AT&T systems, was now projecting an increase of 125,000 to150,000. Comcast also said it expected to increase its cash flow from cable operations this year by about $100 million, to a range of $6.3 billion to $6.4 billion