Changeset 12d3187 for doc/rob_thesis/variadic.tex

Timestamp:

May 1, 2017, 1:39:55 PM (7 years ago)

Author:

Rob Schluntz <rschlunt@…>

Branches:

ADT, aaron-thesis, arm-eh, ast-experimental, cleanup-dtors, deferred_resn, demangler, enum, forall-pointer-decay, jacob/cs343-translation, jenkins-sandbox, master, new-ast, new-ast-unique-expr, new-env, no_list, persistent-indexer, pthread-emulation, qualifiedEnum, resolv-new, with_gc

Children:

2055098

Parents:

b3d70eba

Message:

final revisions to thesis

File:

• doc/rob_thesis/variadic.tex (modified) (4 diffs)

doc/rob_thesis/variadic.tex

@@ -5 +5 @@
 \section{Design Criteria} % TODO: better section name???
 C provides variadic functions through the manipulation of @va_list@ objects.
-A variadic function is one which contains at least one parameter, followed by @...@ as the last token in the parameter list.
-In particular, some form of \emph{argument descriptor} is needed to inform the function of the number of arguments and their types.
+In C, a variadic function is one which contains at least one parameter, followed by @...@ as the last token in the parameter list.
+In particular, some form of \emph{argument descriptor} or \emph{sentinel value} is needed to inform the function of the number of arguments and their types.
 Two common argument descriptors are format strings or counter parameters.
-It is important to note that both of these mechanisms are inherently redundant, because they require the user to explicitly specify information that the compiler already knows.
+It is important to note that both of these mechanisms are inherently redundant, because they require the user to explicitly specify information that the compiler already knows \footnote{While format specifiers can convey some information the compiler does not know, such as whether to print a number in decimal or hexadecimal, the number of arguments is wholly redundant.}.
 This required repetition is error prone, because it is easy for the user to add or remove arguments without updating the argument descriptor.
 In addition, C requires the programmer to hard code all of the possible expected types.
@@ -152 +152 @@
 That is to say, the programmer who writes @sum@ does not need full program knowledge of every possible data type, unlike what is necessary to write an equivalent function using the standard C mechanisms.
 
+\begin{sloppypar}
 Going one last step, it is possible to achieve full generality in \CFA, allowing the summation of arbitrary lists of summable types.
 \begin{cfacode}
@@ -170 +171 @@
 \end{cfacode}
 The \CFA translator requires adding explicit @double ?+?(int, double)@ and @double ?+?(double, int)@ functions for this call to work, since implicit conversions are not supported for assertions.
+\end{sloppypar}
 
 A notable limitation of this approach is that it heavily relies on recursive assertions.
@@ -226 +228 @@
 In the call to @new@, @Array@ is selected to match @T@, and @Params@ is expanded to match @[int, int, int, int]@. To satisfy the assertions, a constructor with an interface compatible with @void ?{}(Array *, int, int, int)@ must exist in the current scope.
 
-The @new@ function provides the combination of type-safe @malloc@ with a constructor call, so that it becomes impossible to forget to construct dynamically-allocated objects.
+The @new@ function provides the combination of polymorphic @malloc@ with a constructor call, so that it becomes impossible to forget to construct dynamically-allocated objects.
 This approach provides the type-safety of @new@ in \CC, without the need to specify the allocated type, thanks to return-type inference.