作者netsm (小黑)
看板C_Sharp
标题[问题] 请教 null 的用法
时间Wed Jan 8 01:16:12 2014
请教各位高手，下面的写法是甚麽意思?
谢谢!
if (Math.Abs(t - 0.3) < dt / 2)
{
write("..\\(2D)u" + filename + ".plt", u);
write("..\\(2D)uexact_" + filename + ".plt", null);
}
//////
public static void write(string fname, fun ux)
{
FileStream fs = new FileStream(fname, FileMode.Create);
StreamWriter sw = new StreamWriter(fs, Encoding.Default);
sw.WriteLine("VARIABLES=x, y, u1");
sw.WriteLine("ZONE T=\"dx={0}, dy={1}\", I={2}, J={3}, F=POINT",
dx, dy, Ni/2, Nj);
for (double y = 0; y <= MaxY; y += dy)
for (double x = 0; x <= MaxX; x += dx)
{
double uk=(ux==null)? (exact(t,x,y)): ux.f1(0, x, y, 0, 0, 0);
sw.WriteLine("{0},{1},{2}", x, y, uk);
}
sw.Close();
}
请教: double uk=(ux==null)? (exact(t,x,y)): ux.f1(0, x, y, 0, 0, 0);
是甚麽样的逻辑?
我读出来的档案 write("..\\(2D)uexact_" + filename + ".plt", null);
只有时间t有值，而x,y皆为零，是否与 null 有关?
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