Reading whitespace separated strings from stdin?

[TheGag96 via Digitalmars-d-learn]

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


1 2 3 # $
4 3 * ! #
20 3 / # $ #
62 # $
2 3 8 * + #
4 48 4 2 + / #
SUM # $
1 2 3 4 5 #
R #
@

...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.

Re: Reading whitespace separated strings from stdin?

[Adam D. Ruppe via Digitalmars-d-learn]

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?

Re: Reading whitespace separated strings from stdin?

[TheGag96 via Digitalmars-d-learn]

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...

Re: Reading whitespace separated strings from stdin?

[Adam D. Ruppe via Digitalmars-d-learn]

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.

Re: Reading whitespace separated strings from stdin?

[weaselcat via Digitalmars-d-learn]

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...


1 2 3 # $
4 3 * ! #
20 3 / # $ #
62 # $
2 3 8 * + #
4 48 4 2 + / #
SUM # $
1 2 3 4 5 #
R #
@

...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);
}

["1", "2", "3", "#", "$", "4", "3", "*", "!", "#", "20", "3", 
"/", "#", "$", "#", "62", "#", "$", "2", "3", "8", "*", "+", "#", 
"4", "48", "4", "2", "+", "/", "#", "SUM", "#", "$", "1", "2", 
"3", "4", "5", "#", "R", "#", "@"]

Re: Reading whitespace separated strings from stdin?

[TheGag96 via Digitalmars-d-learn]

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!