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I think that this is a not so hard to solve question. The main reason why a developer is a good developer is «his interest on programming». A good developer always has a great interest in programming, so probably he will write a blog on programming, he will have a Github or Sourceforge account with his own projects, or even he will be participating on some open source project or programming forum — like StackOverflow — where you can appreciate his activity. If not, he will have his own side projects and he will be able to show you some demo on his computer using some application like Skype or TeamViewer, and he will be able to show his capacity with that side project. Another option is to send you a sample source code file, where both of you must keep the secret. Finally on the interview, you can challenge him to solve a programming problem, where he must prove his capacity with some simple task, like using an algorithm to solve a very specific problem.

A Monoid is a well known abstraction where you have an operation or function, a neutral element and a set that can be operated with that operation or function. Given that description, on Haskell you have an already defined Monoid class which is implemented on common types like Strings. The main monoidal String operation is the concatenation, using the (++) operation, so can have a clear example of the given description in the code that follows.

The Presentation-Abstraction-Control architectural pattern is widely used. I prefer this pattern over other patterns like Model-View-Controller, because it does not lack third party component integration and allows better decoupling of components. «The abstraction component retrieves and processes the data, the presentation component formats the visual and audio presentation of data, and the control component handles things such as the flow of control and communication between the other two components». As you see it has three main layers, as MVC does, but this pattern allows integration of third party components and it is not limited to database models. Think on such applications using third party APIs, where you are not using a Model, ideally you are designing an abstraction to that API to be integrated in your application. Here the PAC patter fits much better than MVC.

A component in an object oriented system is a modular part of the system, where it has required and provided interfaces. On any system design each component should preserve its atomicity, without overloading its functionalities. This means that every component should have a unique set of interfaces to provide and a unique set of interfaces to request from its environment, avoiding duplication and providing the proper reusability. Non atomic components are not so reusable as atomic ones, because they cannot be connected in other tasks. For example if you have an LDAP interface and you want to send SMS notifications to mobile numbers on the directory, you should not plug the SMS notification into the LDAP component, it should be another separate component.

Haskell is a purely functional language with a strong-static typing system. That does not means that you cannot build a compiler using Haskell, and you have a wide variety of compiler constructions libraries and tools. The one that I use in many cases is Parsec. Parsec is a monadic combinator based parser generator that can be modified in runtime, and you do not compile its specification, because it is written directly in Haskell using its set of combinators, providing a very dynamic behavior and allowing a wide variety of possible implementations. Recently on the blog www.programando.org, was launched a challenge to construct a DSL parser for L-System specifications.

There are several parallel models. One of the most used parallel programming models is the threading model, where you create threads or lightweight processes which are sharing memory and resources, like open files. A thread is an independent execution space that shares memory with its creator inside the its parent process. So, imagine that you need to process 5 files containing call time duration and you need to sum and join that data. Processing that set of files sequentially probably is slower than doing a parallel program to process all files at once. Here is an example written in Python that can help you to understand a threaded solution for this problem.

I always wanted to be a programmer. As programmer my main motivations are three main items: challenging problems, good inputs — computers, printers, and related stuff — and well done stuff. Not necessary in that order. Including more than money. Challenging problems are those problems that can make you think a lot on how to solve them, where you need to take your books about algorithms and make some research on how to solve them, mainly related to algorithm design. Good inputs allow you to make a better work, more efficient working hours and comfortable job. Well done stuff, is all your job made well, with the proper milestones, without pressure and doing a great work with algorithms implemented with beautiful code.