On Fri, 3 May 2002, Morten Gulbrandsen wrote:
You forgot an important part:
writeln(output, 'TYPE SOME CHARACTERS AND ');
writeln(output, 'TERMINATE A STRING WITH A *');
repeat
ind := 0;
if eoln(input) then readln(input);
Here, when you haven't typed anything yet, the program will wait for input. The reason is that eoln() doesn't know whether it's the end of the line if there is no input (since the next character might or might not be a return). Further, the input is line buffered. This means that
a) you call eoln()
b) eoln will detect that the input buffer is empty and will call a procedure to read a line, which will read all characters from the keyboard until the first "enter" (that's what line buffering means) c) after you press enter, eoln will start scanning the input buffer. It will find the enter and return true.
d) since eoln returned true, readln is called, which will read/remove all characters from the input buffer until the first enter. So the input buffer is empty again and you're back at square one.
while not eoln(input)
do begin
read(input, ch);
So here, the first time the input buffer is empty and we wait again for input, which explains why you have to press enter twice.
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if not eoln(input)
then begin
ind := ind + 1;
line[ind] := ch;
end;
end;
Can I modify eoln with some compiler option ?
No. It's just a procedure in the system unit, it's not a special language construct or so.
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complete sample program is attached.
It is from a textbook written for UCSD Apple Pascal
I think apple has \n\r\f as cr windows has \n\r and linux has only
\n
as cr, but I don't know if this is relevant.
Mac uses \r, but that doesn't matter indeed , that's all handled transparently.
Jonas
