\chapter[chap:conclusions]{Conclusions}
-At the end of this research, we have created a system called Cλash, which
-allows us to translate hardware descriptions written in Haskell to be
-translated to \VHDL, and be programmed into an FPGA.
+The product of this research is a system called Cλash, which allows hardware
+descriptions written in Haskell to be translated to \VHDL and be programmed
+into an \small{FPGA}.
In this research, we have seen that a functional language is well suited
for hardware descriptions. Function applications provide elegant notation for
case expressions, if expressions) are well suited to describe conditional
assigment in the hardware.
-Useful features from the functional perspective, like polymorphism and higher
-order functions and expressions also prove suited to describe hardware
-and our implementation shows that they can be translated to \VHDL as
-well.
+Useful features from the functional perspective, like polymorphism and
+higher-order functions and expressions also prove suitable to describe
+hardware and our implementation shows that they can be translated to
+\VHDL\ as well.
-Using Haskell as as source language in this research has proven
-fruitful. It has enabled creating a prototype rapidly, to experiment
-with various language features in Cλash. Even supporting more complex
-features like polymorphism and higher order values has been possible. If
-a new language and compiler would have been designed from scratch, that
-language would not have been nearly as advanced as current Cλash.
+A prototype compiler was created in this research. For this prototype the
+Haskell language was chosen as the input language, instead of creating a new
+language from scratch. This has enabled creating the prototype rapidly,
+allowing for experimenting with various functional language features and
+interpretations in Cλash. Even supporting more complex features like
+polymorphism and higher-order values has been possible. If a new language and
+compiler would have been designed from scratch, that new language would not
+have been nearly as advanced as the current version of Cλash.
However, Haskell might not have been the best choice for describing
hardware. Some of the expressiveness it offers is not appropriate for
The lack of real dependent typing support in Haskell has been a burden.
Haskell provides the tools to create some type level programming
-constructs (and is improving fast), but other language might have
-support for more advanced dependent types (and even type level
-operations) as a fundamental part of the language. The need for
-dependent typing is particularly present in Cλash to be able to fix some
-properties (list length, recursion depth, etc.) at compile time. Having
-better support for dependent typing might allow the use of typesafe
-recursion in Cλash, though this is fundamentally still a hard problem.
+constructs (and is improving fast), but another language might have
+support for more advanced dependent types (and even type level operations) as
+a fundamental part of the language. The need for dependent typing is
+particularly present in Cλash to be able to fix some properties (list length,
+recursion depth, etc.) at compile time. Having better support for dependent
+typing might allow the use of typesafe recursion in Cλash, though this is
+fundamentally still a hard problem.
The choice of describing state very explicitly as extra arguments and
results is a mixed blessing. It provides very explicit specification of
easy modification of the description in our normalization program, since
state can be handled just like other arguments and results.
-On the other hand, the explictness of the states and in particular
+On the other hand, the explicitness of the states and in particular
substates, mean that more complex descriptions can become cumbersome
-very quick. One finds that dealing with unpacking, passing, receiving
+very quickly. One finds that dealing with unpacking, passing, receiving
and repacking becomes tedious and even errorprone. Removing some of this
boilerplate would make the language even easier to use.
On the whole, the usefulness of Cλash for describing hardware is not
-completely clear yet. Most elements of the language haven proven
+completely clear yet. Most elements of the language have proven
suitable, and even a real world hardware circuit (the reducer \todo{ref
christiaan}) has been implemented. However, the language has not been
used during a complete design process, where its rapid prototyping and
boilerplate or synchronicity limitations could become real problems.
It is expected that Cλash will be used as a tool in education at the
-University of Twente soon, hopefully this will provide a better insight
+University of Twente soon. Hopefully this will provide a better insight
in how the system performs.
-The general design of the prototype (A frontend that desugares into a
-small, but functional and typed language, a transformation
-system that works on this small language, and a simple backend) has
-worked well and should probably be preserved. Especially the
-transformation based normalization system is suitable. It is easy to
-program a transformation in the prototype, though it is not trivial to
-maintain enough overview to guarantee that the system is correct and
-complete. In fact, the current set of transformations is probably not
-complete yet, in particular when stateful descriptions are involved.
-However, the system can be (and has been) described in a mathematical
-sense, allowing us to reason about it and probably also prove various
-correctness properties in the future.
+The prototype compiler has a clear design. Its frontend is taken from the \GHC\
+compiler and desugars Haskell into a small, but functional and typed
+language, called \emph{Core}. Cλash adds a transformation system that reduces
+this small language to a normal form and a simple backend that performs a
+direct translation to \VHDL. This approach has worked well and should probably
+be preserved. Especially the transformation based normalization system is
+suitable. It is easy to implement a transformation in the prototype, though it
+is not trivial to maintain enough overview to guarantee that the system is
+correct and complete. In fact, the current set of transformations is probably
+not complete yet, in particular when stateful descriptions are involved.
+However, the system can be (and has been) described in a mathematical sense,
+allowing us to reason about it and probably also prove various correctness
+properties in the future.
-The scope of this research has been limited to structural descriptions
-that are synchronous in a single clock domain using cycle accurate
-designs. Even though this is a broad spectrum already, it may turn out
-that this scope is too narrow for practical use of Cλash. Most people
-that hear about using a functional language for hardware description
-instantly hope to be able to provide a concise mathematical description
-of their algorithm and have the hardware generated for them. Since this
-is obviously a different problem alltogether, we could not have hoped to
-even start solving it. However, hopefully the current Cλash system
-provides a solid base on top of which further experimentation with
-functional descriptions can be built.
+The scope of this research has been limited to structural descriptions that
+are synchronous in a single clock domain using cycle accurate designs. Even
+though this is a broad spectrum already, it may turn out that this scope is
+too narrow for practical use of Cλash. A common response from people that hear
+about using a functional language for hardware description is that they hope
+to be able to provide a concise mathematical description of their algorithm
+and have the hardware generated for them. Since this is obviously a different
+problem altogether, we could not have hoped to even start solving it. However,
+hopefully the current Cλash system provides a solid base on top of which
+further experimentation with functional descriptions can be built.
projects / matthijs / master-project / report.git / blobdiff