What's the point of DSLs / fluent interfaces

Question

I was recently watching a webcast about how to create a fluent DSL and I have to admit, I don\'t understand the reasons why one would use such an approach (at least for the give

Answer 1

2 - Is this fluent interface approach just a replacement for the non existing named method parameters in C#? Would named parameters make fluent interfaces obsolete, e.g. something similar objective-C offers:

Well yes and no. The fluent interface gives you a larger amount of flexibility. Something that could not be achieved with named params is:

sizer.FromImage(i)
 .ReduceByPercent(x)
 .Pixalize()
 .ReduceByPercent(x)
 .OutputImageFormat(ImageFormat.Jpeg)
 .ToLocation(o)
 .Save();

The FromImage, ToLocation and OutputImageFormat in the fluid interface, smell a bit to me. Instead I would have done something along these lines, which I think is much clearer.

 new Sizer("bob.jpeg") 
 .ReduceByPercent(x)
 .Pixalize()
 .ReduceByPercent(x)
 .Save("file.jpeg",ImageFormat.Jpeg);

Fluent interfaces have the same problems many programming techniques have, they can be misused, overused or underused. I think that when this technique is used effectively it can create a richer and more concise programming model. Even StringBuilder supports it.

var sb = new StringBuilder(); 
sb.AppendLine("Hello")
 .AppendLine("World");