\stopcombination
}
- The first step in the core to \small{VHDL} translation process, is normalization. We
- aim to bring the core description into a simpler form, which we can
+ The first step in the Core to \small{VHDL} translation process, is normalization. We
+ aim to bring the Core description into a simpler form, which we can
subsequently translate into \small{VHDL} easily. This normal form is needed because
- the full core language is more expressive than \small{VHDL} in some
+ the full Core language is more expressive than \small{VHDL} in some
areas (higher-order expressions, limited polymorphism using type
- classes, etc.) and because core can describe expressions that do not
+ classes, etc.) and because Core can describe expressions that do not
have a direct hardware interpretation.
\section{Normal form}
Now we have some intuition for the normal form, we can describe how we want
the normal form to look like in a slightly more formal manner. The
EBNF-like description in \in{definition}[def:IntendedNormal] captures
- most of the intended structure (and generates a subset of \GHC's core
+ most of the intended structure (and generates a subset of \GHC's Core
format).
There are two things missing from this definition: cast expressions are
\subsection[sec:normalization:uniq]{Binder uniqueness}
A common problem in transformation systems, is binder uniqueness. When not
considering this problem, it is easy to create transformations that mix up
- bindings and cause name collisions. Take for example, the following core
+ bindings and cause name collisions. Take for example, the following Core
expression:
\startlambda
function type. Since these can be any expression, there is no
transformation needed. Note that this category is exactly all
expressions that are not transformed by the transformations for the
- previous two categories. This means that \emph{any} core expression
+ previous two categories. This means that \emph{any} Core expression
that is used as an argument to a built-in function will be either
transformed into one of the above categories, or end up in this
categorie. In any case, the result is in normal form.
there are probably expressions involving cast expressions that cannot
be brought into intended normal form by this transformation system.
- The uses of casts in the core system should be investigated more and
+ The uses of casts in the Core system should be investigated more and
transformations will probably need updating to handle them in all
cases.
our compilation to \VHDL. The main difference seems to be that in
hardware every expression is always evaluated, while in software
it is only evaluated if needed, but it should be possible to
- assign a meaning to core expressions that assumes neither.
+ assign a meaning to Core expressions that assumes neither.
Since each of the transformations can be applied to any
subexpression as well, there is a constraint on our meaning
By systematically reviewing the entire Core language definition
along with the intended normal form definition (both of which have
a similar structure), it should be possible to identify all
- possible (sets of) core expressions that are not in intended
+ possible (sets of) Core expressions that are not in intended
normal form and identify a transformation that applies to it.
This approach is especially useful for proving completeness of our
}
Considering that we required a prototype which should be working quickly,
and that implementing parsers, semantic checkers and especially
- typcheckers is not exactly the core of this research (but it is lots and
+ typcheckers is not exactly the Core of this research (but it is lots and
lots of work!), using an existing language is the obvious choice. This
also has the advantage that a large set of language features is available
to experiment with and it is easy to find which features apply well and
Assuming that we do not want to deal with (or modify) parsing, typechecking
and other frontend business and that native code is not really a useful
format anymore, we are left with the choice between the full Haskell
- \small{AST}, or the smaller (simplified) core representation.
+ \small{AST}, or the smaller (simplified) Core representation.
The advantage of taking the full \small{AST} is that the exact structure
of the source program is preserved. We can see exactly what the hardware
the full \small{AST} is a very complicated datastructure. If we are to
handle everything it offers, we will quickly get a big compiler.
- Using the core representation gives us a much more compact datastructure
- (a core expression only uses 9 constructors). Note that this does not mean
- that the core representation itself is smaller, on the contrary.
- Since the core language has less constructs, most Core expressions
+ Using the Core representation gives us a much more compact datastructure
+ (a Core expression only uses 9 constructors). Note that this does not mean
+ that the Core representation itself is smaller, on the contrary.
+ Since the Core language has less constructs, most Core expressions
are larger than the equivalent versions in Haskell.
- However, the fact that the core language is so much smaller, means it is a
+ However, the fact that the Core language is so much smaller, means it is a
lot easier to analyze and translate it into something else. For the same
- reason, \small{GHC} runs its simplifications and optimizations on the core
+ reason, \small{GHC} runs its simplifications and optimizations on the Core
representation as well \cite[jones96].
We will use the normal Core representation, not the simplified Core. Even
translates Haskell sources to a typed Core representation.
\stopdesc
\startdesc{Normalization}
- This is a step that transforms the core representation into a normal
- form. This normal form is still expressed in the core language, but has
+ This is a step that transforms the Core representation into a normal
+ form. This normal form is still expressed in the Core language, but has
to adhere to an additional set of constraints. This normal form is less
- expressive than the full core language (e.g., it can have limited
+ expressive than the full Core language (e.g., it can have limited
higher-order expressions, has a specific structure, etc.), but is
also very close to directly describing hardware.
\stopdesc
\startdesc{\small{VHDL} generation}
- The last step takes the normal formed core representation and generates
+ The last step takes the normal formed Core representation and generates
\small{VHDL} for it. Since the normal form has a specific, hardware-like
structure, this final step is very straightforward.
\stopdesc
any functions used by the entry functions (recursively).
\section[sec:prototype:core]{The Core language}
- \defreftxt{core}{the Core language}
+ \defreftxt{Core}{the Core language}
Most of the prototype deals with handling the program in the Core
language. In this section we will show what this language looks like and
how it works.
for normal function \quote{calls}, but also for applying type
abstractions and data constructors.
- In core, there is no distinction between an operator and a
+ In Core, there is no distinction between an operator and a
function. This means that, for example the addition of two numbers
looks like the following in Core:
\startdesc{Note}
The Core language in \small{GHC} allows adding \emph{notes}, which serve
- as hints to the inliner or add custom (string) annotations to a core
+ as hints to the inliner or add custom (string) annotations to a Core
expression. These should not be generated normally, so these are not
handled in any way in the prototype.
\stopdesc
(though you could of course construct invalidly typed expressions
through the \GHC\ API).
- Any type in core is one of the following:
+ Any type in Core is one of the following:
\startdesc{A type variable}
\startlambda
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