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digitalmars.D.learn - Formatted input from text file

reply IK <istvan.karolyi rocketmail.com> writes:
I'm attempting Project Euler's problem 11.
http://projecteuler.net/problem=11

Currently, my code looks like posted below, and it gives
    object.Error: Access Violation
at runtime.

Question: how to read that grid from a text file? (See link above.)
If you have ideas for using something other than uint[20][20], please say.
Thank you.

import std.stdio;
import std.stream;

void main()
{
	uint[20][20] grid;
	BufferedFile input_file;

	input_file.open("p011_input.txt");
	input_file.readf("%(%(%d %)\n%)", grid);
}
Jun 18 2012
next sibling parent reply "bearophile" <bearophileHUGS lycos.com> writes:
IK:

 Question: how to read that grid from a text file?

I don't know the cause of your problem. While investigating it I have filed another bug: http://d.puremagic.com/issues/show_bug.cgi?id=8260 In the meantime this (a bit scary) code solves your reading problem: import std.stdio, std.algorithm, std.range, std.conv; void main() { const grid = File("table.txt") .byLine().map!(r => std.algorithm.splitter(r) .map!(to!int)() .array())() .array(); writeln(grid); } Bye, bearophile
Jun 18 2012
parent reply IK <istvan.karolyi rocketmail.com> writes:
Hmm does your code generate a 1D `array` as a grid, bearophile?
Anyway thanks, I'll compile it shortly.

My own code evolved to what's below and gives a Range violation.
Also I don't understand why formattedRead can't just accept a casted
`opSlice.dup`, is it a bug?

void main()
{
	uint[20][20] grid;
	auto input_file = new MmFile("p011_input.txt");
	string temp = cast(string)input_file.opSlice;

	formattedRead(temp, "%(%(%s %)\n%)", &grid);
}
Jun 18 2012
parent Timon Gehr <timon.gehr gmx.ch> writes:
On 06/18/2012 05:11 PM, IK wrote:
 Hmm does your code generate a 1D `array` as a grid, bearophile?
 Anyway thanks, I'll compile it shortly.

 My own code evolved to what's below and gives a Range violation.
 Also I don't understand why formattedRead can't just accept a casted
 `opSlice.dup`, is it a bug?

Yes.
 void main()
 {
 	uint[20][20] grid;
 	auto input_file = new MmFile("p011_input.txt");
 	string temp = cast(string)input_file.opSlice;

 	formattedRead(temp, "%(%(%s %)\n%)",&grid);
 }

IIRC formattedRead would require input similar to "[[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5],[1,2,3,4,5]]" This works: void main() { auto input_file = new MmFile("p011_input.txt"); auto text = cast(string)input_file[]; auto grid = text.splitLines.map!(_=>_.split.to!(uint[])).array; }
Jun 18 2012
prev sibling next sibling parent "IK" <istvan.karolyi rocketmail.com> writes:
This program below fails if the file contains an empty line.
Why exactly does this happen?
Does ln get a mangled value when a line is empty?


     import std.format;
     import std.stdio;

     void main()
     {
         int[] test;

         foreach (ln; File("ints.txt").byLine)
             formattedRead(ln, "%(%d %)", &test);

         writefln("%(%d %)", test);
     }


std.conv.ConvException c:\dmd2\windows\bin\..\..\src\phobos\std\conv.d(1779): 
Unexpected '
' when converting from type char[] to type int
----------------
4169C4
41684F
405E63
405BDF
405A06
405964
40573F
4055CE
40246B
4020CC
4083A0
4083DA
407FFB
41DB21
----------------
Jun 19 2012
prev sibling next sibling parent "IK" <istvan.karolyi rocketmail.com> writes:
Now I see! The error message is a bit awkward, it should show 
'\n' instead.
(It should also use Windows line endings on a Windows machine, 
but that's a minor point.)

So indeed formattedRead() fails for a newline. Can this be 
considered a bug?
Jun 19 2012
prev sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
IK:

 So indeed formattedRead() fails for a newline. Can this be 
 considered a bug?

Hara knows. Maybe it's a bug. Bye, bearophile
Jun 19 2012