Changeset 3628765 for doc/proposals/concurrency/text/cforall.tex

Timestamp:

Oct 4, 2017, 3:31:34 PM (6 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, aaron-thesis, arm-eh, 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:

b7778c1

Parents:

dcfc4b3

Message:

More work on chapter 2 and 3

File:

• doc/proposals/concurrency/text/cforall.tex (modified) (1 diff)

doc/proposals/concurrency/text/cforall.tex

@@ -100 +100 @@
 Note that like \CC, \CFA introduces \code{new} and \code{delete}, which behave like \code{malloc} and \code{free} in addition to constructing and destructing objects, after calling \code{malloc} and before calling \code{free} respectively.
 
+\section{Parametric Polymorphism}
+Routines in \CFA can also be reused for multiple types. This is done using the \code{forall} clause which gives \CFA it's name. \code{forall} clauses allow seperatly compiled routines to support generic usage over multiple types. For example, the following sum function will work for any type which support construction from 0 and addition :
+\begin{cfacode}
+//constraint type, 0 and +
+forall(otype T | { void ?{}(T *, zero_t); T ?+?(T, T); })
+T sum(T a[ ], size_t size) {
+        T total = 0;                            //construct T from 0
+        for(size_t i = 0; i < size; i++)
+                total = total + a[i];   //select appropriate +
+        return total;
+}
+
+S sa[5];
+int i = sum(sa, 5);                             //use S's 0 construction and +
+\end{cfacode}
+
+Since writing constraints on types can become cumbersome for more constrained functions, \CFA also has the concept of traits. Traits are named collection of constraints which can be used both instead and in addition to regular constraints:
+\begin{cfacode}
+trait sumable( otype T ) {
+        void ?{}(T *, zero_t);          //constructor from 0 literal
+        T ?+?(T, T);                            //assortment of additions
+        T ?+=?(T *, T);
+        T ++?(T *);
+        T ?++(T *);
+};
+forall( otype T | sumable(T) )  //use trait
+T sum(T a[], size_t size);
+\end{cfacode}
+
+\section{with Clause/Statement}
+Since \CFA lacks the concept of a receiver, certain functions end-up needing to repeat variable names often, to solve this \CFA offers the \code{with} statement which opens an aggregate scope making its fields directly accessible (like Pascal).
+\begin{cfacode}
+struct S { int i, j; };
+int mem(S & this) with this             //with clause
+        i = 1;                                          //this->i
+        j = 2;                                          //this->j
+}
+int foo() {
+        struct S1 { ... } s1;
+        struct S2 { ... } s2;
+        with s1                                         //with statement
+        {
+                //access fields of s1
+                //without qualification
+                with s2                                 //nesting
+                {
+                        //access fields of s1 and s2
+                        //without qualification
+                }
+        }
+        with s1, s2                             //scopes open in parallel
+        {
+                //access fields of s1 and s2
+                //without qualification
+        }
+}
+\end{cfacode}
+
 For more information on \CFA see \cite{cforall-ug,rob-thesis,www-cfa}.