Changeset 804b57e


Ignore:
Timestamp:
Feb 2, 2018, 3:28:14 PM (4 years ago)
Author:
Aaron Moss <a3moss@…>
Branches:
aaron-thesis, arm-eh, cleanup-dtors, deferred_resn, demangler, jacob/cs343-translation, jenkins-sandbox, master, new-ast, new-ast-unique-expr, new-env, no_list, persistent-indexer, resolv-new, with_gc
Children:
d7d4702
Parents:
0188a0b
Message:

Fix conversion of feature paper to article format; stub in added sections on ctors, references, with-stmt

Location:
doc
Files:
1 added
1 edited

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  • doc/papers/general/Paper.tex

    r0188a0b r804b57e  
    148148The C programming language is a foundational technology for modern computing with millions of lines of code implementing everything from commercial operating-systems to hobby projects.
    149149This installation base and the programmers producing it represent a massive software-engineering investment spanning decades and likely to continue for decades more.
    150 The \cite{TIOBE} ranks the top 5 most popular programming languages as: Java 16\%, \Textbf{C 7\%}, \Textbf{\CC 5\%}, \Csharp 4\%, Python 4\% = 36\%, where the next 50 languages are less than 3\% each with a long tail.
     150The TIOBE\cite{TIOBE} ranks the top 5 most popular programming languages as: Java 16\%, \Textbf{C 7\%}, \Textbf{\CC 5\%}, \Csharp 4\%, Python 4\% = 36\%, where the next 50 languages are less than 3\% each with a long tail.
    151151The top 3 rankings over the past 30 years are:
    152152\lstDeleteShortInline@%
     
    185185\label{sec:poly-fns}
    186186
    187 \CFA{}\hspace{1pt}'s polymorphism was originally formalized by \cite{Ditchfield92}, and first implemented by \cite{Bilson03}.
     187\CFA{}\hspace{1pt}'s polymorphism was originally formalized by Ditchfield\cite{Ditchfield92}, and first implemented by Bilson\cite{Bilson03}.
    188188The signature feature of \CFA is parametric-polymorphic functions~\cite{forceone:impl,Cormack90,Duggan96} with functions generalized using a @forall@ clause (giving the language its name):
    189189\begin{lstlisting}
     
    258258}
    259259\end{lstlisting}
    260 Within the block, the nested version of @<@ performs @>@ and this local version overrides the built-in @<@ so it is passed to @qsort@.
     260Within the block, the nested version of @?<?@ performs @?>?@ and this local version overrides the built-in @?<?@ so it is passed to @qsort@.
    261261Hence, programmers can easily form local environments, adding and modifying appropriate functions, to maximize reuse of other existing functions and types.
    262262
     
    337337% While a nominal-inheritance system with associated types could model one of those two relationships by making @El@ an associated type of @Ptr@ in the @pointer_like@ implementation, few such systems could model both relationships simultaneously.
    338338
    339 
    340339\section{Generic Types}
    341340
     
    466465However, the \CFA type-checker ensures matching types are used by all calls to @?+?@, preventing nonsensical computations like adding a length to a volume.
    467466
    468 
    469467\section{Tuples}
    470468\label{sec:tuples}
     
    544542p`->0` = 5;                                                                     $\C{// change quotient}$
    545543bar( qr`.1`, qr );                                                      $\C{// pass remainder and quotient/remainder}$
    546 rem = [42, div( 13, 5 )]`.0.1`;                         $\C{// access 2nd component of 1st component of tuple expression}$
     544rem = [div( 13, 5 ), 42]`.0.1`;                         $\C{// access 2nd component of 1st component of tuple expression}$
    547545\end{lstlisting}
    548546
     
    730728\end{lstlisting}
    731729Hence, function parameter and return lists are flattened for the purposes of type unification allowing the example to pass expression resolution.
    732 This relaxation is possible by extending the thunk scheme described by~\cite{Bilson03}.
     730This relaxation is possible by extending the thunk scheme described by Bilson\cite{Bilson03}.
    733731Whenever a candidate's parameter structure does not exactly match the formal parameter's structure, a thunk is generated to specialize calls to the actual function:
    734732\begin{lstlisting}
     
    901899\end{comment}
    902900
     901\section{Improved Procedural Paradigm}
     902
     903It is important to the design team that \CFA subjectively ``feel like'' C to user programmers.
     904An important part of this subjective feel is maintaining C's procedural programming paradigm, as opposed to the object-oriented paradigm of other systems languages such as \CC and Rust.
     905Maintaining this procedural paradigm means that coding patterns that work in C will remain not only functional but idiomatic in \CFA, reducing the mental burden of retraining C programmers and switching between C and \CFA development.
     906Nonetheless, some features of object-oriented languages are undeniably convienient, and the \CFA design team has attempted to adapt them to a procedural paradigm so as to incorporate their benefits into \CFA; two of these features are resource management and name scoping.
     907
     908\subsection{Constructors and Destructors}
     909
     910One of the strengths of C is the control over memory management it gives programmers, allowing resource release to be more consistent and precisely timed than is possible with garbage-collected memory management.
     911However, this manual approach to memory management is often verbose, and it is useful to manage resources other than memory (\eg file handles) using the same mechanism as memory.
     912\CC is well-known for an approach to manual memory management that addresses both these issues, Resource Allocation Is Initialization (RAII), implemented by means of special \emph{constructor} and \emph{destructor} functions; we have implemented a similar feature in \CFA.
     913
     914\TODO{Fill out section. Mention field-constructors and at-equal escape hatch to C-style initialization. Probably pull some text from Rob's thesis for first draft.}
     915
     916\subsection{@with@ Statement}
     917
     918In any programming language, some functions have a naturally close relationship with a particular data type.
     919Object-oriented programming allows this close relationship to be codified in the language by making such functions \emph{class methods} of their related data type.
     920Class methods have certain privileges with respect to their associated data type, notably un-prefixed access to the fields of that data type.
     921When writing C functions in an object-oriented style, this un-prefixed access is swiftly missed, as access to fields of a @Foo* f@ requires an extra three characters @f->@ every time, which disrupts coding flow and clutters the produced code.
     922
     923\TODO{Fill out section. Be sure to mention arbitrary expressions in with-blocks, recent change driven by Thierry to prioritize field name over parameters.}
     924
     925\section{References}
     926
     927\TODO{Pull draft text from user manual; make sure to discuss nested references and rebind operator drawn from }
    903928
    904929\section{Evaluation}
     
    10131038In contrast, \CFA has a single facility for polymorphic code supporting type-safe separate-compilation of polymorphic functions and generic (opaque) types, which uniformly leverage the C procedural paradigm.
    10141039The key mechanism to support separate compilation is \CFA's \emph{explicit} use of assumed properties for a type.
    1015 Until \CC~\cite{C++Concepts} are standardized (anticipated for \CCtwenty), \CC provides no way to specify the requirements of a generic function in code beyond compilation errors during template expansion;
     1040Until \CC concepts~\cite{C++Concepts} are standardized (anticipated for \CCtwenty), \CC provides no way to specify the requirements of a generic function in code beyond compilation errors during template expansion;
    10161041furthermore, \CC concepts are restricted to template polymorphism.
    10171042
     
    10211046In \CFA terms, all Cyclone polymorphism must be dtype-static.
    10221047While the Cyclone design provides the efficiency benefits discussed in Section~\ref{sec:generic-apps} for dtype-static polymorphism, it is more restrictive than \CFA's general model.
    1023 \cite{Smith98} present Polymorphic C, an ML dialect with polymorphic functions and C-like syntax and pointer types; it lacks many of C's features, however, most notably structure types, and so is not a practical C replacement.
    1024 
    1025 \cite{obj-c-book} is an industrially successful extension to C.
     1048Smith and Volpano~\cite{Smith98} present Polymorphic C, an ML dialect with polymorphic functions, C-like syntax, and pointer types; it lacks many of C's features, however, most notably structure types, and so is not a practical C replacement.
     1049
     1050Objective-C~\cite{obj-c-book} is an industrially successful extension to C.
    10261051However, Objective-C is a radical departure from C, using an object-oriented model with message-passing.
    10271052Objective-C did not support type-checked generics until recently \cite{xcode7}, historically using less-efficient runtime checking of object types.
    1028 The~\cite{GObject} framework also adds object-oriented programming with runtime type-checking and reference-counting garbage-collection to C;
     1053The GObject~\cite{GObject} framework also adds object-oriented programming with runtime type-checking and reference-counting garbage-collection to C;
    10291054these features are more intrusive additions than those provided by \CFA, in addition to the runtime overhead of reference-counting.
    1030 \cite{Vala} compiles to GObject-based C, adding the burden of learning a separate language syntax to the aforementioned demerits of GObject as a modernization path for existing C code-bases.
     1055Vala~\cite{Vala} compiles to GObject-based C, adding the burden of learning a separate language syntax to the aforementioned demerits of GObject as a modernization path for existing C code-bases.
    10311056Java~\cite{Java8} included generic types in Java~5, which are type-checked at compilation and type-erased at runtime, similar to \CFA's.
    10321057However, in Java, each object carries its own table of method pointers, while \CFA passes the method pointers separately to maintain a C-compatible layout.
    10331058Java is also a garbage-collected, object-oriented language, with the associated resource usage and C-interoperability burdens.
    10341059
    1035 D~\cite{D}, Go, and~\cite{Rust} are modern, compiled languages with abstraction features similar to \CFA traits, \emph{interfaces} in D and Go and \emph{traits} in Rust.
     1060D~\cite{D}, Go, and Rust~\cite{Rust} are modern, compiled languages with abstraction features similar to \CFA traits, \emph{interfaces} in D and Go and \emph{traits} in Rust.
    10361061However, each language represents a significant departure from C in terms of language model, and none has the same level of compatibility with C as \CFA.
    10371062D and Go are garbage-collected languages, imposing the associated runtime overhead.
     
    10541079\CCeleven introduced @std::tuple@ as a library variadic template structure.
    10551080Tuples are a generalization of @std::pair@, in that they allow for arbitrary length, fixed-size aggregation of heterogeneous values.
    1056 Operations include @std::get<N>@ to extract vales, @std::tie@ to create a tuple of references used for assignment, and lexicographic comparisons.
     1081Operations include @std::get<N>@ to extract values, @std::tie@ to create a tuple of references used for assignment, and lexicographic comparisons.
    10571082\CCseventeen proposes \emph{structured bindings}~\cite{Sutter15} to eliminate pre-declaring variables and use of @std::tie@ for binding the results.
    10581083This extension requires the use of @auto@ to infer the types of the new variables, so complicated expressions with a non-obvious type must be documented with some other mechanism.
     
    10681093The goal of \CFA is to provide an evolutionary pathway for large C development-environments to be more productive and safer, while respecting the talent and skill of C programmers.
    10691094While other programming languages purport to be a better C, they are in fact new and interesting languages in their own right, but not C extensions.
    1070 The purpose of this paper is to introduce \CFA, and showcase two language features that illustrate the \CFA type-system and approaches taken to achieve the goal of evolutionary C extension.
     1095The purpose of this paper is to introduce \CFA, and showcase language features that illustrate the \CFA type-system and approaches taken to achieve the goal of evolutionary C extension.
    10711096The contributions are a powerful type-system using parametric polymorphism and overloading, generic types, and tuples, which all have complex interactions.
    10721097The work is a challenging design, engineering, and implementation exercise.
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