A Simple Web Crawler in Perl

What's a web crawler? A web crawler is "a internet bot that systematically browses the World Wide Web, typically for the purpose of web indexing".

Well, I got bored one night and decided to write one in Perl.

Here's the result:

Github

If you want to use it, you have the following options:

Q: Want to ask something about the crawler? Leave a comment!

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GrandTrunk Currency API in C#

Today I just finished a client API for the GrandTrunk historic currency conversion web service.

The web service allows the following:

• Getting a list of the supported currencies according to a specified date
• Converting a currency to another according to the rate of a specified date
• Retrieving a list of conversion rates between 2 currencies according to a specified time interval.

If you are interested in using it, you can find it on Github.

Here's how you can use it:

	using System;
	using System.Collections.Generic;
	using IsKernel.Api.Pool.Currency;
	namespace GrandTrunkCurrenciesApiExample
	{
	class Program
	{
	public static void Main(string[] args)
	{
	DateTime olderDate = new DateTime(1997,3,1);
	DateTime startDate = new DateTime(2011,3,1);
	DateTime stopDate = new DateTime(2011,5,1);
	//List of supported currencies at this momment
	Console.WriteLine("List of supported currencies at this moment: ");
	List<string> listOfCurrencies
	= GrandTrunkCurrencyConversionService
	.Instance.GetListOfSupportedCurrencies();
	DisplayList(listOfCurrencies);
	//List of supported currencies in 01-03-1997
	Console.WriteLine("List of supported currencies in 01-03-1997: ");
	List<string> olderListOfCurrencies
	= GrandTrunkCurrencyConversionService
	.Instance.GetListOfSupportedCurrencies(olderDate);
	DisplayList(olderListOfCurrencies);
	//The USD (US Dollar) - AUD (Australian Dollar) rate today
	Console.WriteLine("The USD-AUD rate today");
	ConversionRate usdToAud = GrandTrunkCurrencyConversionService
	.Instance
	.GetConversionRate("USD","AUD");
	Console.WriteLine("In {0} : 1 {1} = {3} {2}",
	usdToAud.Date,
	usdToAud.FromCurrency,
	usdToAud.ToCurrency,
	usdToAud.Rate);
	//The USD (US Dollar) - AUD (Australian Dollar) rate in 01-03-1997
	Console.WriteLine("The USD-AUD rate in 01-03-1997");
	ConversionRate olderUsdToAud = GrandTrunkCurrencyConversionService
	.Instance
	.GetConversionRate("USD","AUD",
	olderDate);
	Console.WriteLine("In {0} : 1 {1} = {3} {2}",
	olderUsdToAud.Date,
	olderUsdToAud.FromCurrency,
	olderUsdToAud.ToCurrency,
	olderUsdToAud.Rate);
	//The USD (US Dollar) - AUD (Australian Dollar) rate between
	//01.03.2011 - 01.05.2011
	Console.WriteLine("The USD-AUD rate between 01-03-2011 and " +
	"01-05-2011");
	List<ConversionRate> conversionRateList
	= GrandTrunkCurrencyConversionService.Instance
	.GetConversionRate("USD","AUD", startDate, stopDate);
	DisplayConversionList(conversionRateList);
	Console.Read();
	}
	private static void DisplayList(List<string> list)
	{
	foreach (string element in list)
	{
	Console.WriteLine(element);
	}
	}
	private static void DisplayConversionList(List<ConversionRate> list)
	{
	foreach (ConversionRate element in list)
	{
	Console.WriteLine("In {0} : 1 {1} = {3} {2}",
	element.Date,
	element.FromCurrency,
	element.ToCurrency,
	element.Rate);
	}
	}
	}
	}

view raw CSharp_GrandTrunkCurrencyConversionApi_Example.cs hosted with ❤ by GitHub

You can find the library on:

Github

Q: Do you know other free web services which provide similar features? Leave me a link!

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Always Obtaining a Future Date in C#

I was working today on building a C# REST client for a historic currency conversion web service and needed to write the unit tests.

A historic currency conversion web service it is a web service that allows the retrieval of the exchange rate of 2 currencies from a specified past date. In order to prevent the user from sending a bad data to the service, I employed some simple measures to verify the user input.

In order to simulate error cases in the unit tests I needed to find a method to create a date that will always be in the future. Below you can see my solution:

	//The RIGHT way
	[Test]
	public void GetConversionRate_DateFutureParameter_ThrowsException()
	{
	//This will always return a date that will be in the future
	DateTime future = DateTime.Now.AddYears(1);
	Assert.Throws( typeof(CurrencyConversionException),
	() => GrandTrunkCurrencyConversionService.Instance
	.GetConversionRate(TEST_CURRENCY_NAME_US_DOLLAR,
	TEST_CURRENCY_NAME_AU_DOLLAR,
	future) );
	}
	//The NOT SO RIGHT way
	[Test]
	public void GetConversionRate_DateFutureParameter_ThrowsException()
	{
	//Perhaps no one will run this unit test in 10 years. But what if
	//someone will?
	DateTime notReallyFuture = new DateTime(2023,1,1);
	Assert.Throws( typeof(CurrencyConversionException),
	() => GrandTrunkCurrencyConversionService.Instance
	.GetConversionRate(TEST_CURRENCY_NAME_US_DOLLAR,
	TEST_CURRENCY_NAME_AU_DOLLAR,
	notReallyFuture) );
	}

view raw CSharp_Nunit_AlwaysObtainAFutureDate_Example.cs hosted with ❤ by GitHub

The main idea is that you will never know for how much time your software will be used, so it's better to play it safe :-).

Q: Since I was talking about past and future, what is the oldest library you wrote and still use today?

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