be converted to an actual netlist format by an (optimizing) \VHDL\ synthesis
tool.
-Besides trivial circuits such as variants of both the FIR filter and the
-simple CPU shown in \Cref{sec:usecases}, the \CLaSH\ compiler has also been
-shown to work for non-trivial descriptions. \CLaSH\ has been able to
+Besides trivial circuits such as variants of both the \acro{FIR} filter and
+the simple \acro{CPU} shown in \Cref{sec:usecases}, the \CLaSH\ compiler has
+also been shown to work for non-trivial descriptions. \CLaSH\ has been able to
successfully translate the functional description of a streaming reduction
circuit~\cite{reductioncircuit} for floating point numbers.
compiler. The \CLaSH\ compiler has generic translation rules to
translated the user-defined types described below.
- The \CLaSH compiler is able to infer unspecified types,
+ The \CLaSH\ compiler is able to infer unspecified types,
meaning that a developer does not have to annotate every function with a
- type signature (though it is good practice to do so anyway).
+ type signature (even if it is good practice to do so).
% Translation of two most basic functional concepts has been
% discussed: function application and choice. Before looking further
the rest of paper is: \hs{[a|n]}. Where the \hs{a} is the element
type, and \hs{n} is the length of the vector. Note that this is
a notation used in this paper only, vectors are slightly more
- elaborate in real \CLaSH programs.
+ elaborate in real \CLaSH\ programs.
% The state type of an 8 element register bank would then for example
% be:
\VHDL\ resembles an actual netlist description and not idiomatic \VHDL.
\section{Use cases}
-
-\subsection{FIR Filter}
\label{sec:usecases}
+\subsection{FIR Filter}
As an example of a common hardware design where the use of higher-order
functions leads to a very natural description is a \acro{FIR} filter, which is
basically the dot-product of two vectors:
\subsection{Higher order CPU}
\begin{code}
-type FuState = State Word
fu :: (a -> a -> a)
- -> [a]:n
- -> (RangedWord n, RangedWord n)
- -> FuState
- -> (FuState, a)
+ -> [a | n]
+ -> (Index (n - 1), Index (n - 1))
+ -> a
+ -> (a, a)
fu op inputs (addr1, addr2) (State out) =
(State out', out)
where
\end{code}
\begin{code}
-type CpuState = State [FuState]:4
+type CpuState = State [Word | 4]
+
cpu :: Word
- -> [(RangedWord 7, RangedWord 7)]:4
+ -> [(Index 6, Index 6) | 4]
-> CpuState
-> (CpuState, Word)
-cpu input addrs (State fuss) =
- (State fuss', out)
+cpu input addrs (State fuss) = (State fuss', out)
where
- fures = [ fu const inputs!0 fuss!0
- , fu (+) inputs!1 fuss!1
- , fu (-) inputs!2 fuss!2
- , fu (*) inputs!3 fuss!3
- ]
- (fuss', outputs) = unzip fures
- inputs = 0 +> 1 +> input +> outputs
- out = head outputs
+ fures = [ fu const inputs (addrs!0) (fuss!0)
+ , fu (+) inputs (addrs!1) (fuss!1)
+ , fu (-) inputs (addrs!2) (fuss!2)
+ , fu (*) inputs (addrs!3) (fuss!3)
+ ]
+ (fuss', outputs) = unzip fures
+ inputs = 0 +> (1 +> (input +> outputs))
+ out = head outputs
\end{code}
\section{Related work}
functional language \acro{ML}, and has support for polymorphic types and
higher-order functions. Published work suggests that there is no direct
simulation support for \acro{HML}, but that a description in \acro{HML} has to
-be translated to \VHDL\ and that the translated description can than be
+be translated to \VHDL\ and that the translated description can then be
simulated in a \VHDL\ simulator. Also not all of the mentioned language
features of \acro{HML} could be translated to hardware. The \CLaSH\ compiler
on the other hand can correctly translate all of the language constructs