Maciej Piechotka

[Java] On Leapyear

2008-10-16T19:05:56-07:00

import java.util.Scanner;

public class LeapYear {

	public static void main(String[] args) {
		
		Scanner in = new Scanner(System.in);

		System.out.println("Please input a year");
		int input = in.nextInt();
		
		if (input % 4 == 0 && (input % 100 != 0 || input % 400 == 0)) {
			System.out.println("The year: " + input + " is a leapyear");
		} else {
			System.out.println("The year: " + input + " is NOT leapyear");
		}
	}
}

[Python] On Permutation of values

2008-10-07T14:34:59-07:00

You looking for cartesian product. Here is a simle solution using generators.

Be aware that the generator is returned not a list (to save memory).

def cart(*lists):
    if not lists:
        for x in L:
            yield [x]
    else:
        for x in L:
            for y in cart(lists[0], *lists[1:]):
                yield [x] + y

def perm(arg):
    if len(arg) == 0:
        return [[]]
    
    a = []
    for i in arg:
        a.append(xrange(i))
    return cart(*a)

[Ruby] On Conditional Assignment

2008-09-21T23:45:48-07:00

@danielharan:

Well - -100 < 10 but (-100)** > 10**2 as 10000 > 100.

@Tien Dung:

Sorry for voting 1 on the second refactoring. I meant 5 but clicked in wrong place. Do anybody knowns how to change it?

[C] On A Java-like function split

2008-09-16T10:42:26-07:00

YAR - it ommits the separators and have much more cleaner structure.

#include <stdlib.h>
#include <string.h>

const int ALLOC_BLOCK = 16;

void
process_escape_block (char **iter, char **out, int *offset, char esp)
{
  char *begin, *end;

  begin = *iter;
  while(**iter != esp)
    (*iter)++;
  end = (*iter)++;

  *out = realloc(*out, *offset + (end - begin) + 1);
  strncpy(*out + *offset, begin, end - begin);
  *offset = *offset + (end - begin);
}

char *
process_block (char **iter, const char sep, const char esp)
{
  char *out;
  int   len;

  out = NULL;
  len = 0;

  while(1)
    {
      char *begin, *end;

      begin = *iter;
      while(**iter != sep && **iter != esp && **iter != '\0')
        (*iter)++;
      end = *iter;

      out = realloc(out, len + (end - begin) + 1);
      strncpy(out + len, begin, end - begin);
      len += (end - begin);
      
      if(**iter == esp)
      	{
      	  (*iter)++;
      	  process_escape_block(iter, &out, &len, esp);
      	}
      else if(**iter == sep)
      	{
      	  (*iter)++;
      	  break;
      	}
      else
      	{
      	  break;
      	}
    }
  return out;
}

char **
split (char *str, const char sep, const char esc)
{
  const int ALLOC_BLOCK = 16;
  
  char     **ret;
  int        ret_alloc;
  int        ret_iter;
  char      *iter;

  ret = NULL;
  ret_alloc = 0;
  ret_iter = 0;
  
  iter = str;
  while(1)
    {
      if(ret_iter == ret_alloc)
      	{
      	  ret_alloc += ALLOC_BLOCK;
      	  ret = realloc(ret, ret_alloc);
      	}

      if(*iter == '\0')
      	break;
      
      ret[ret_iter++] = process_block(&iter, sep, esc);
    }
  ret[ret_iter] = NULL;

  return ret;
}

[C] On A Java-like function split

2008-09-16T10:06:49-07:00

May be something like that? The addition of error-checking should be relativly easy (removed to be clear).

I'm not sure what your code do - especially with the memory allocation:
ret = (char **) malloc (sizeof (char *)); // Array of string of size 1?
ret[nParts] = (char *) malloc (sizeof (char)); // String of size 0? ("\0")

#include <stdlib.h>
#include <string.h>

const int ALLOC_BLOCK = 16;

char **
split (char *str, const char sep, const char esc)
{
  char **ret;        /* Allocated block */
  int    ret_alloc;  /* How much we allocated */
  int    ret_iter;   /* The current pointer index */
  char  *iter;       /* The current character */
  char  *iter_begin; /* The start of current */
  int    in_escape;  /* If currently in escape block */

  /* Initial allocation */
  ret_alloc = ALLOC_BLOCK;
  ret = malloc(sizeof(char *) * ret_alloc);
  ret_iter = 0;

  /* Main loop */
  iter = str;
  iter_begin = iter;
  in_escape = 0;
  while(1)
    {
      if(*iter == esc) /* If escape character */
  	    {
  	      if(in_escape)
  	        in_escape = 1;
      	  else
      	    in_escape = 0;
      	}
      else if(*iter == sep || *iter == 0) /* If separator */
      	{
      	  /* Copy from the beginning */
      	  ret[ret_iter++] = strndup(iter_begin, iter - iter_begin);
      	  /* Allocate block if near empty */
      	  if(ret_iter == ret_alloc)
      	    {
      	      ret_alloc += ALLOC_BLOCK;
      	      ret = realloc(NULL, sizeof(char *) * ret_alloc);
      	    }
      	  if (*iter) /* If it is not the end */
      	    {
      	      iter_begin = (iter + 1);
      	    }
      	  else /* It is the end */
      	    {
      	      break;
      	    }
      	}
      else
      	{
      	  /* Do nothing */
      	}
      iter++;
    }
  ret[ret_iter] = NULL; /* Terminating NULL */
  return ret;
}

[Java] On fileContentsEquals

2008-08-19T08:14:37-07:00

I'm tring once more - I've posted 3 minutes after the orginal post but it get spammed:

private static boolean areSame(File f1, File f2) throws IOException
{
  if(f1 == f2)
    return true;
  if(f1 == null || f2 == null)
    return false;

  MappedByteBuffer buf1 = new FileInputStream(f1).getChannel().map(FileChannel.MapMode.READ_ONLY, 0, f1.length);
  MappedByteBuffer buf2 = new FileInputStream(f2).getChannel().map(FileChannel.MapMode.READ_ONLY, 0, f1.length);
  return buf1.equals(buf2);
}

[Ruby] On simple pluralize

2008-08-19T08:09:27-07:00

Only in the i18n/l10n frameworks.

However it allows you keep things dry:

## Helper

def pluralize(string, length)
  if length > 1
    string.pluralize
  else
    string
  end
end

## View

<%= pluralize("Favorites", @resource.favorites.length) %>

[Java] On fileContentsEquals

2008-08-18T10:40:38-07:00

1. Yes. It will work on bytes
2. May be something like that - 3 lines in NIO.

public static boolean fileContentsEquals(File file1, File file2) throws IOException {
  ByteBuffer buf1 = new FileInputStream(file1).getChannel().map(MapMode.READ_ONLY, 0, file1.length());
  ByteBuffer buf2 = new FileInputStream(file2).getChannel().map(MapMode.READ_ONLY, 0, file2.length());
  return buf1.equals(buf2);
}

[Ruby] On CSV turn in to an array of hashes

2008-08-15T08:47:51-07:00

May be something like that:

require 'enumerator'

def fix_send_to_array(array)
  recipients = []
  array.split(',').each_cons(2) do |arr|
    recipients << {:name => arr[0], :email => arr[1]}
  end
end

[Ruby] On Split an array into half

2008-08-14T13:45:19-07:00

The same rounding:

artists = [1, 2, 3]
column_1 = artists[0...(artists.size/2.0).ceil]
column_2 = artists[(artists.size/2.0).ceil...artists.size]

[Ruby] On Split an array into half

2008-08-14T13:41:51-07:00

Something like that (a bit different rounding):

artists = [1, 2, 3]
column_1 = artists[0, artists.size/2]
column_2 = artists[artists.size/2...artists.size]

[Ruby] On Caesar Cipher

2008-08-10T18:43:08-07:00

Modification of Fabien Jakimowicz's code

def caesar(text, shift)
  text.split('').collect! {|letter| (letter[0] + shift).chr}.join
end

[Ruby] On Same function repeated but with diff global vars!

2008-08-08T21:39:42-07:00

May be something like that:

PS. Usage of global variables is not recommended.

%w{user network thumbnail}.each do |obj|
  module_eval <<-"EOS", __FILE__, __LINE__
    def #{obj}_path(path)
      rpp = $#{obj}_remote_pictures_paths
      pre = rpp[digest(path, rpp.length)]
      "\#{pre}/\#{path}"
    end
  EOS
end

[PHP] On PHP5 Database Clas

2008-08-06T21:23:18-07:00

Sorry for late response - so what do you want which is not covered by MySQLi?

[Ruby] On showing records in Ascending or Descening order on click

2008-08-06T14:00:10-07:00

Why you don't use JavaScript? You will have it wothout even hitting server.
You can of course fallback to hitting server.

Do not use session for storing objects. You ask for problems (mostly performance problems).

## Users controller
class UsersController < ApplicationController

  def index
    by = %w{age salary}.include? params['by'] ? params['by'] : 'age'
    dir = %w{ASC DESC}.include? params['dir'] ? params['dir'] : 'DESC'
    @users = User.find(:all, :order => "#{by} #{dir}")
  end
end

[Ruby] On showing records in Ascending or Descening order on click

2008-08-06T13:54:55-07:00

Why you don't use JavaScript?
Just sort the data on user page without hitting the database or even server.

[Ruby] On Rails - Multiple instances and folder creation

2008-08-03T09:02:18-07:00

May be something like that?

PS. Shouldn't short-name be called permalink?

## app/controller/accounts_controller.rb

 require 'FileUtils'

  def create
    @account = Account.create!(params[:account])
    @website = @account.websites.create!(params[:website])
    @user = @account.users.create!(params[:user])

    flash[:notice] = 'Your account was successfully created. Please login to begin :)'
    redirect_to login_path
  rescue RecordNotSaved
    render :layout => 'signup', :action => 'new'
  end

## In models (each)
  attr_protected :short_name
  before_create :set_short_name
  
  def set_short_name
    self.short_name ||= self.name.gsub(/\W+|\s+/, '-').downcase
  end

## In account model
  after_create :create_dir
    
  def create_dir
    FileUtils.mkdir_p("public/content/#{self.short_name}")
  end

## In website model
  belongs_to :account

  after_create :create_dir
    
  def create_dir
    %w{docs pictures users}.each do |d|
      FileUtils.mkdir_p("public/content/#{self.account.short_name}/#{self.short_name}/#{d}")
    end
  end

[Ruby] On Find the Intersection of Arrays with a Hash

2008-08-01T07:03:53-07:00

The sort is unnecessary in my code

pools = {1 => [1,2,3], 2=> [3,4,5], 3=> [5,6,7]}
rej = Hash.new {0}
pools.values.flatten.reject! {|elem| rej[elem]++ != 1}

[Ruby] On Find the Intersection of Arrays with a Hash

2008-07-31T22:03:29-07:00

May be something like that

pools = {1 => [1,2,3], 2=> [3,4,5], 3=> [5,6,7]}
rej = Hash.new {0}
pools.values.flatten.sort.reject! {|elem| rej[elem]++ != 1}

[Ruby] On Brainfuck Generator in Ruby

2008-07-31T20:31:29-07:00

A little bit different working - but in 3 lines

# generate_bf.rb
# (copyleft) Matt Gauger 2008
# Randomly generates a brainfuck program
# Commandline argument is used as the length of the program
# Otherwise, the program defaults to 140 characters in length to fit on Twitter

# generated Brainfuck code not guaranteed to do anything !!

length = ARGV.last.to_i || 140
chars = %w{< > + - . , [ ]}
puts Array.new(length) {chars[rand(chars.length)]}.join

[Ruby] On Exercise: Deaf Grandma

2008-07-30T18:55:16-07:00

@Wolfbyte - to keep the ruby convention: 'granny_can_hear' shouldn't be named 'granny_hear?'?

[Ruby] On Contoller refactoring

2008-07-30T11:46:33-07:00

Do it RESTful. Use fat models. It is very hard to do it in other way in RoR/Merb/... Create invitation model without any DB table associated (i.e. fake model).

Alternativly you can send email in the constructor

## app/model/invitation.rb
class Invitation
  include Validatable

  attr_accessor ...

  def initialize(*args)
    ... # Set the parameters
  end

  def save
    if valid?
      send_email # Have to return non-0/non-nil on success
    else
      false
    end
  end
  
  def save!
    save || raise ProperException
  end
end

[Ruby] On Exercise: Deaf Grandma

2008-07-29T20:28:57-07:00

Only what within the task. You can change puts into whatever you want.

count_bye = 0
loop do
  word = gets.chomp

  if word == "BYE" 
    count_bye += 1
    if count_bye == 3
      puts "Bye son."
      break
    end
  else
    count_bye = 0
  end

  if word != "BYE" and word.upcase == word
    puts "No. Not since #{1930 + rand(21)}."
  else
    puts "I cannot hear you son!"
  end
end

[PHP] On PHP5 Database Clas

2008-07-21T19:24:17-07:00

1. Why not PEAR DB?
2. Why not MySQLi with precompiled queries (it has everything you need but faster and in standard)?

[Ruby] On Constructing a search query

2008-07-07T14:55:37-07:00

DON'T DO IT!
It is broken by design - you can easily inject SQL Code into it.

PS. What it has in common with ferret?