Haskell an obvious choice.
\section[sec:prototype:output]{Output format}
- The second important question is: What will be our output format?
+ The second important question is: what will be our output format?
This output format should at least allow for programming the
hardware design into a field-programmable gate array (\small{FPGA}).
The choice of output format is thus limited by what hardware
func arg
\stoplambda
This is function application. Each application consists of two
- parts: The function part and the argument part. Applications are used
+ parts: the function part and the argument part. Applications are used
for normal function \quote{calls}, but also for applying type
abstractions and data constructors.
A case expression evaluates its scrutinee, which should have an
algebraic datatype, into weak head normal form (\small{WHNF}) and
- (optionally) binds it to \lam{bndr}. Every alternative lists a
- single constructor (\lam{C0 ... Cn}). Based on the actual
- constructor of the scrutinee, the corresponding alternative is
- chosen. The binders in the chosen alternative (\lam{bndr0,0 ....
- bndr0,m} are bound to the actual arguments to the constructor in
- the scrutinee.
+ (optionally) binds it to \lam{bndr}. If bndr is wild, \refdef{wild
+ binders} it is left out. Every alternative lists a single constructor
+ (\lam{C0 ... Cn}). Based on the actual constructor of the scrutinee, the
+ corresponding alternative is chosen. The binders in the chosen
+ alternative (\lam{bndr0,0 .... bndr0,m} are bound to the actual
+ arguments to the constructor in the scrutinee.
This is best illustrated with an example. Assume
there is an algebraic datatype declared as follows\footnote{This
\stopdesc
Using this set of types, all types in basic Haskell can be represented.
-
\todo{Overview of polymorphism with more examples (or move examples
- here)}.
+ here)}
\section[sec:prototype:statetype]{State annotations in Haskell}
As noted in \in{section}[sec:description:stateann], Cλash needs some
Word} and \hs{Word} types by pattern matching and by using the explicit
the \hs{State constructor}.
- This explicit conversion makes the \VHDL\ generation easier: Whenever we
+ This explicit conversion makes the \VHDL\ generation easier: whenever we
remove (unpack) the \hs{State} type, this means we are accessing the
current state (\eg, accessing the register output). Whenever we are a
adding (packing) the \hs{State} type, we are producing a new value for
(state) variables} and \emph{substate variables}, which will be
defined in the rules themselves.
+ These rules describe everything that can be done with state
+ variables and state-containing variables. Everything else is
+ invalid.
+
\startdesc{State variables can appear as an argument.}
\startlambda
avg = λi.λspacked. ...
function.
Fortunately, the \lam{accs'} variable (and any other substate) has a
- property that we can easily check: It has a \lam{State} type
+ property that we can easily check: it has a \lam{State} type
annotation. This means that whenever \VHDL\ is generated for a tuple
(or other algebraic type), we can simply leave out all elements that
have a \lam{State} type. This will leave just the parts of the state
\stoplambda
When we would really leave out the crossed out parts, we get a slightly
- weird program: There is a variable \lam{s} which has no value, and there
+ weird program: there is a variable \lam{s} which has no value, and there
is a variable \lam{s'} that is never used. Together, these two will form
the state process of the function. \lam{s} contains the "current" state,
\lam{s'} is assigned the "next" state. So, at the end of each clock
\stopbuffer
\placeexample[][ex:AccStateVHDL]{\VHDL\ generated for acc from \in{example}[ex:AvgState]}
- {\typebuffer[AccStateVHDL]}
+ {\typebuffervhdl{AccStateVHDL}}
\placeexample[][ex:AvgStateVHDL]{\VHDL\ generated for avg from \in{example}[ex:AvgState]}
- {\typebuffer[AvgStateVHDL]}
+ {\typebuffervhdl{AvgStateVHDL}}
% \subsection{Initial state}
% How to specify the initial state? Cannot be done inside a hardware
% function, since the initial state is its own state argument for the first
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