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digitalmars.D.learn - Reading whitespace separated strings from stdin?

reply "TheGag96" <thegag96 gmail.com> writes:
Hi guys! I had this homework assignment for data structures that 
has a pretty easy solution in C++. Reading input like this...










 

...where " " denotes the end of input is fairly simple in C++:

string token = "";
while (token != " ") {
   //handle input
}

Note that having newlines doesn't matter at all; every token is 
just assumed to be separated by "whitespace". However in D, I 
looked around could not find a solution better than this:

foreach (line; stdin.byLine) {
   foreach (token; line.split) {
     //handle input
   }
}

Is there any way to do this without two loops/creating an array? 
"readf(" %d", &token);" wasn't cutting it either.

Thanks.
Apr 20 2015
next sibling parent reply "Adam D. Ruppe" <destructionator gmail.com> writes:
I think this should work:

import std.stdio;

void main() {
         string token;
         while(readf("%s ", &token))
                 writeln(token);
}


Have you tried that? What is wrong with it if you have?
Apr 20 2015
parent reply "TheGag96" <thegag96 gmail.com> writes:
On Tuesday, 21 April 2015 at 01:46:53 UTC, Adam D. Ruppe wrote:

 I think this should work:

 import std.stdio;

 void main() {
         string token;
         while(readf("%s ", &token))
                 writeln(token);
 }


 Have you tried that? What is wrong with it if you have?


It'll just leave some trailing whitespace, which I don't want. 
And somehow doing token = token.stip STILL leaves that whitespace 
somehow...
Apr 20 2015
parent "Adam D. Ruppe" <destructionator gmail.com> writes:
On Tuesday, 21 April 2015 at 02:04:24 UTC, TheGag96 wrote:

 It'll just leave some trailing whitespace, which I don't want.


oh it also keeps the newlines attached. Blargh.

Well, forget the D functions, just use the C functions:

import core.stdc.stdio;

void main() {
         char[16] token;
         while(scanf("%15s", &token) != EOF)
                 printf("**%s**\n", token.ptr);
}



You could convert to a string if needed with import std.conv; 
to!string(token.ptr), but if you can avoid that, you should, this 
loop has no allocations which is a nice thing.
Apr 20 2015
prev sibling parent reply "weaselcat" <weaselcat gmail.com> writes:
On Tuesday, 21 April 2015 at 01:31:58 UTC, TheGag96 wrote:

 Hi guys! I had this homework assignment for data structures 
 that has a pretty easy solution in C++. Reading input like 
 this...










  

 ...where " " denotes the end of input is fairly simple in C++:

 string token = "";
 while (token != " ") {
   //handle input
 }

 Note that having newlines doesn't matter at all; every token is 
 just assumed to be separated by "whitespace". However in D, I 
 looked around could not find a solution better than this:

 foreach (line; stdin.byLine) {
   foreach (token; line.split) {
     //handle input
   }
 }

 Is there any way to do this without two loops/creating an 
 array? "readf(" %d", &token);" wasn't cutting it either.

 Thanks.


import std.stdio;
import std.array;
void main(){
     auto tokens = stdin.readln(' ').split;
     writeln(tokens);
}
Apr 20 2015
parent "TheGag96" <thegag96 gmail.com> writes:
On Tuesday, 21 April 2015 at 03:44:16 UTC, weaselcat wrote:

 snip


Wow, that's a damn good solution... I didn't know that readln() 
could take an argument that it stops at once it finds.

Now the thing is, this program is supposed to be a reverse Polish 
notation calculator. A human using this program would probably be 
confused as to why nothing happens when they hit enter after a 
line -- it only really works in the context of copying and 
pasting the whole input in. Still a really neat solution to know 
anyhow. Thanks!
Apr 22 2015