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can't readf to the same variable twice

For this simple code:

long l;
readf("%d", &l);
readf("%d", &l);

when I enter 20 as the second number it throws an exception

exception: std.conv.ConvException@/usr/include/dlang/dmd/std/conv.d(1995):

Unexpected '2' when converting from type LockingTextReader to type long

Why is this happening and what am I doing wrong?

Solution

  • There's still a newline sitting in the buffer after the first one that needs to be consumed.

    Similar to what I wrote about here: D lang - Using read and readln() in the same program

    the same fix should work.

    long l;
readf(" %d", &l); // note the leading space
writeln("Got ", l);
readf(" %d", &l); // and again
writeln("Got ", l);