|
|
@@ -12753,8 +12753,8 @@ for tuples become overloaded for use with arrays.}
|
|
|
\python{
|
|
|
The subscript operator becomes overloaded for use with arrays and tuples
|
|
|
and now may appear on the left-hand side of an assignment.
|
|
|
-Note that the index of the subscript may be an arbitrary expression
|
|
|
-and not just a constant integers.
|
|
|
+Note that the index of the subscript, when applied to an array, may be an
|
|
|
+arbitrary expression and not just a constant integer.
|
|
|
The \code{len} function is also applicable to arrays.
|
|
|
}
|
|
|
%
|
|
|
@@ -13170,14 +13170,30 @@ an array:
|
|
|
In the following subsections we provide hints regarding how to update
|
|
|
the passes to handle arrays.
|
|
|
|
|
|
-\subsection{Shrink}
|
|
|
-
|
|
|
+\subsection{Type-based Resolution}
|
|
|
+
|
|
|
+As noted above, with the addition of arrays, several operators have
|
|
|
+become \emph{overloaded}, that is, they can be applied to values of
|
|
|
+more than one type. In this case, the element access and \code{len}
|
|
|
+operators can be applied to both tuples and arrays. This kind of
|
|
|
+overloading is quite common in programming languages, so many
|
|
|
+compilers perform \emph{overload resolution}\index{subject}{overload resolution}
|
|
|
+to handle it. The idea is to translate each overloaded
|
|
|
+operator into different operators for the different types.
|
|
|
+
|
|
|
+Implement a new pass named \code{resolve}.
|
|
|
+Translate the reading of an array element
|
|
|
+into a call to
|
|
|
+\racket{\code{vectorof-ref}}\python{\code{array\_load}}
|
|
|
+and the writing of an array element to
|
|
|
+\racket{\code{vectorof-set!}}\python{\code{array\_store}}
|
|
|
Translate calls to \racket{\code{vector-length}}\python{\code{len}}
|
|
|
-into a primitive specific to arrays, \racket{\code{vectorof-length}}\python{\code{array\_len}},
|
|
|
-when the argument's type is \CARRAYTY{T}.
|
|
|
+into \racket{\code{vectorof-length}}\python{\code{array\_len}}.
|
|
|
+When these operators are applied to tuples, leave them as-is.
|
|
|
%
|
|
|
\python{The type checker for \LangArray{} adds a \code{has\_type}
|
|
|
- field to the argument of \code{len} for this purpose.}
|
|
|
+ field which can be inspected to determine whether the operator
|
|
|
+ is applied to a tuple or an array.}
|
|
|
|
|
|
|
|
|
\subsection{Bounds Checking}
|
|
|
@@ -13254,9 +13270,11 @@ Section~\ref{sec:array-rep}.
|
|
|
The instructions generated for accessing an element of an array differ
|
|
|
from those for a tuple (Section~\ref{sec:select-instructions-gc}) in
|
|
|
that the index is not a constant so the offset must be computed at
|
|
|
-runtime. Also, note that assignment to an array element may appear in
|
|
|
-as a stand-alone statement, so make sure to handle that situation in
|
|
|
-this pass.
|
|
|
+runtime.
|
|
|
+
|
|
|
+%% Also, note that assignment to an array element may appear in
|
|
|
+%% as a stand-alone statement, so make sure to handle that situation in
|
|
|
+%% this pass.
|
|
|
|
|
|
%% Finally, the instructions for \code{any-vectorof-length} should be
|
|
|
%% similar to those for \code{vectorof-length}, except that one must
|
Jeremy Siek