[Haskell-cafe] Constraints at construction

[Iain Barnett]

On 12 Oct 2008, at 9:28 pm, Henning Thielemann wrote:

>
> On Thu, 9 Oct 2008, Iain Barnett wrote:
>
>> If I were to create an object in C#, for instance, I could add  
>> code to the constructor that might limit the type further e.g.
>>
>>
>> public class Car
>> {
>> 	string model;
>> 	int wheels;
>>
>> 	public Car ( string model, int no_of_wheels )
>> 	{
>> 		if (  no_of_wheels <= 2 ) {
>> 			throw new Exception( "a car must have at least 3 wheels");
>> 		}
>> 				this.model = model;
>> 		this.no_of_wheels = no_of_wheels;
>> 	}
>> }
>
> I think it is not the right way to handle the number of wheels with  
> an exception. This should be considered an error.
>    http://www.haskell.org/haskellwiki/Error

Only if you think through the code you're writing - i.e. non  
idiomatic C#   ;)

Iain