\subsection{Types}
Haskell is a statically-typed language, meaning that the type of a
variable or function is determined at compile-time. Not all of Haskell's
- typing constructs have a clear translation to hardware, as such this
- section will only deal with the types that do have a clear correspondence
+ typing constructs have a clear translation to hardware, this section will
+ therefor only deal with the types that do have a clear correspondence
to hardware. The translatable types are divided into two categories:
\emph{built-in} types and \emph{user-defined} types. Built-in types are
those types for which a direct translation is defined within the \CLaSH\
% using translation rules that are discussed later on.
\subsubsection{Built-in types}
- The following types have direct translation defined within the \CLaSH\
+ The following types have direct translations defined within the \CLaSH\
compiler:
\begin{xlist}
\item[\bf{Bit}]
- This is the most basic type available. It can have two values:
- \hs{Low} and \hs{High}.
+ the most basic type available. It can have two values:
+ \hs{Low} or \hs{High}.
% It is mapped directly onto the \texttt{std\_logic} \VHDL\ type.
\item[\bf{Bool}]
- This is a basic logic type. It can have two values: \hs{True}
- and \hs{False}.
+ this is a basic logic type. It can have two values: \hs{True}
+ or \hs{False}.
% It is translated to \texttt{std\_logic} exactly like the \hs{Bit}
% type (where a value of \hs{True} corresponds to a value of
% \hs{High}).
\hs{if-then-else} construct, which requires a \hs{Bool} value for
the condition.
\item[\bf{SizedWord}, \bf{SizedInt}]
- These are types to represent integers. A \hs{SizedWord} is unsigned,
+ these are types to represent integers. A \hs{SizedWord} is unsigned,
while a \hs{SizedInt} is signed. Both are parametrizable in their
size.
% , so you can define an unsigned word of 32 bits wide as follows:
% types are translated to the \VHDL\ \texttt{unsigned} and
% \texttt{signed} respectively.
\item[\bf{Vector}]
- This is a vector type that can contain elements of any other type and
+ this is a vector type that can contain elements of any other type and
has a fixed length. The \hs{Vector} type constructor takes two type
arguments: the length of the vector and the type of the elements
contained in it. The short-hand notation used for the vector type in
% \hs{RegisterState} type is a vector of 8 32-bit words. A fixed size
% vector is translated to a \VHDL\ array type.
\item[\bf{Index}]
- This is another type to describe integers, but unlike the previous
+ this is another type to describe integers, but unlike the previous
two it has no specific bit-width, but an upper bound. This means that
its range is not limited to powers of two, but can be any number.
An \hs{Index} only has an upper bound, its lower bound is
data-types with the \hs{data} keyword, type synonyms with the \hs{type}
keyword and datatype renaming constructs with the \hs{newtype} keyword.
\GHC\ offers a few more advanced ways to introduce types (type families,
- existential typing, {\small{GADT}}s, etc.) which are not standard Haskell.
+ existential typing, {\acro{GADT}}s, etc.) which are not standard Haskell.
As it is currently unclear how these advanced type constructs correspond
- with hardware, they are for now unsupported by the \CLaSH\ compiler
+ to hardware, they are for now unsupported by the \CLaSH\ compiler.
Only an algebraic datatype declaration actually introduces a
- completely new type. Type synonyms and renaming constructs only define new
+ completely new type. Type synonyms and type renaming only define new
names for existing types, where synonyms are completely interchangeable
- and renaming constructs need explicit conversions. Therefore, these do not
+ and type renaming requires explicit conversions. Therefore, these do not
need any particular translation, a synonym or renamed type will just use
the same representation as the original type. For algebraic types, we can
make the following distinctions:
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