Changeset 41fcd94 for doc/papers/general
- Timestamp:
- Feb 8, 2018, 4:52:56 PM (7 years ago)
- 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:
- ff878b7
- Parents:
- 06b176d (diff), eb7f20c (diff)
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doc/papers/general/Paper.tex
r06b176d r41fcd94 1444 1444 In \CFA, the address of a @T&@ is a lvalue @T*@, as the address of the underlying @T@ is stored in the reference, and can thus be mutated there. 1445 1445 The result of this rule is that any reference can be rebound using the existing pointer assignment semantics by assigning a compatible pointer into the address of the reference, \eg @&r1 = &x;@ above. 1446 This rebinding can occur to an arbitrary depth of reference nesting; $n$ address-of operators applied to a reference nested $m$ times will produce an lvalue pointer nested $n$ times if $n \le m$ (note that $n = m+1$ is simply the usual C rvalue address-of operator applied to the $n = m$ case). 1447 The explicit address-of operators can be thought of as ``cancelling out'' the implicit dereference operators, \eg @(&`*`)r1 = &x@ or @(&(&`*`)`*`)r3 = &(&`*`)r1@ or even @(&`*`)r2 = (&`*`)`*`r3@ for @&r2 = &r3@. 1446 This rebinding can occur to an arbitrary depth of reference nesting; loosely speaking, nested address-of operators will produce an lvalue nested pointer up to as deep as the reference they're applied to. 1447 These explicit address-of operators can be thought of as ``cancelling out'' the implicit dereference operators, \eg @(&`*`)r1 = &x@ or @(&(&`*`)`*`)r3 = &(&`*`)r1@ or even @(&`*`)r2 = (&`*`)`*`r3@ for @&r2 = &r3@. 1448 More precisely: 1449 \begin{itemize} 1450 \item 1451 if @R@ is an rvalue of type {@T &@$_1 \cdots$@ &@$_r$} where $r \ge 1$ references (@&@ symbols) than @&R@ has type {@T `*`&@$_{\color{red}2} \cdots$@ &@$_{\color{red}r}$}, \\ \ie @T@ pointer with $r-1$ references (@&@ symbols). 1452 1453 \item 1454 if @L@ is an lvalue of type {@T &@$_1 \cdots$@ &@$_l$} where $l \ge 0$ references (@&@ symbols) then @&L@ has type {@T `*`&@$_{\color{red}1} \cdots$@ &@$_{\color{red}l}$}, \\ \ie @T@ pointer with $l$ references (@&@ symbols). 1455 \end{itemize} 1448 1456 1449 1457 Since pointers and references share the same internal representation, code using either is equally performant; in fact the \CFA compiler converts references to pointers internally, and the choice between them in user code can be made based solely on convenience. … … 1480 1488 In particular, \CFA does not implement class-based encapsulation: neither the constructor nor any other function has privileged access to the implementation details of a type, except through the translation-unit-scope method of opaque structs provided by C. 1481 1489 1482 In \CFA, a constructor is a function named @?{}@, while a destructor is a function named @^?{}@; like other \CFA operators, these names represent the syntax used to call the constructor or destructor, \eg @ S s = { ... };@ or @^(s){};@.1490 In \CFA, a constructor is a function named @?{}@, while a destructor is a function named @^?{}@; like other \CFA operators, these names represent the syntax used to call the constructor or destructor, \eg @x{ ... };@ or @^x{};@. 1483 1491 Every constructor and destructor must have a return type of @void@, and its first parameter must have a reference type whose base type is the type of the object the function constructs or destructs. 1484 1492 This first parameter is informally called the @this@ parameter, as in many object-oriented languages, though a programmer may give it an arbitrary name. … … 1533 1541 \begin{cfa} 1534 1542 Array a, b; 1535 (a){};$\C{// default construct}$1536 (b){ a }; $\C{// copy construct}$1537 ^ (a){};$\C{// destruct}$1538 (a){ 5, 0xFFFFFFFF }; $\C{// explicit constructor call}$1543 a{}; $\C{// default construct}$ 1544 b{ a }; $\C{// copy construct}$ 1545 ^a{}; $\C{// destruct}$ 1546 a{ 5, 0xFFFFFFFF }; $\C{// explicit constructor call}$ 1539 1547 \end{cfa} 1540 1548
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