On 06/22/2011 09:30 AM, Ali Çehreli wrote:
On Wed, 22 Jun 2011 14:57:57 +0000, GreatEmerald wrote:
This should be a very elementary question. How do you get a string off
stdin? Or an integer, or a boolean, for that matter? If I use this:
float MyFloat;
string MyString;
readf("%f",&MyFloat);
writeln(MyFloat);
readf("%s",&MyString);
writeln(MyString);
I get the float printed correctly, but when it asks to input the string,
whatever I input gets ignored - I can't reach the writeln part in any
way and I have to forcibly close the program. The same thing is with
ints - if I enter an int, it acts as if I didn't enter anything at all.
But floats work fine for some reason. Any thoughts about what is
happening there?
I'm using openSUSE 11.4 and DMD 2.053.
Reading from an input stream is sometimes confusing.
Things to remember:
- Use %s for any type unless there is reason not to
- The line terminator from the previous entry is still in the input. (You
may call readf(" ") to flush those white space characters. (I've just
discovered this.))
- string can hold any character including space and the line terminator.
That's why pressing the Enter doesn't terminate reading a string.
- Use a space character before any format specifier to ignore zero or
more whitespace characters before the previous input: " %s".
- To read a string (actually a line), use chomp(readln())
- I don't know whether this is intended and I don't think that we should
routinely use this: The EOF (Ctrl-D on Unix consoles, Ctrl-Z on Windows)
terminates reading the string but strangely not the entire input.
import std.stdio;
import std.string;
void main()
{
float MyFloat;
readf(" %s",&MyFloat);
writeln(MyFloat);
readf(" ");
string MyString = chomp(readln());
writeln(MyString);
}
Ali
Remember that readf is reading characters, and converting them to types
for you. I've just gotten in the habbit of reading in the string, and
then parsing the string on my own. Readf doesn't grant me anything
special that I can't do on my own. It's easy enough to do something like
this:
[kai.meyer@kai-rhel6 sandbox]$ cat d_read.d
import std.stdio;
import std.string;
import std.conv;
void main()
{
string[] buffer;
int a;
float b;
string c;
buffer = chomp(readln()).split(" ");
a = to!(int)(buffer[0]);
b = to!(float)(buffer[1]);
c = buffer[2..$].join(" ");
writef("Read in: '%d' '%f' '%s'\n", a, b, c);
}
If I type:
1 1.3 this is a string
On the command line after the execution, I get this back:
Read in: '1' '1.300000' 'this is a string'
It's not very stream-ish, because readln breaks on a new line. You could
call the "buffer = chomp..." line again if (buffer.length == 0) before
you attempt another conversion.
