学习编译原理

				{递归调用测试}
				{功能：对于输入n,输出n的阶乘}
				program sd
				var integer s;
				    integer t;
				procedure factor(integer n;var integer m);
				var integer w;
				begin
				if n=0
				then m:=1
				else 
				  factor(n-1,w);
				  m:=n*w
				fi
				end
				begin
				read(s);
				factor(s,t);
				write(t)
				end.