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view interps/rail/src/Var.h @ 6558:4ad4b893c806
<b_jonas> learn links are one of the very few HTML renderers that don\'t try to store a full document tree with heavyweight objects for each node just in case javascript wants to modify it later, so it\'s the only engine that can render those HTMLs that are automatically converted from a PDF and put each letter to a separate element.
author | HackBot |
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date | Thu, 14 Jan 2016 11:54:35 +0000 |
parents | 859f9b4339e6 |
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// Var.h // This is the base class for all variables in rail. The // acquire/release is for reference counting, which we will use for // our GC implementation. We can use reference counting here because // the only primitives are cons (':'), lambda ('&'), and stack // operations. No modifications of cons cells or closures are allowed. // The simple tag-based polymorphism here is used because all of the // actions work only on specific well-defined types. Thus we want // to bypass the complex multiple-dispatch pattern. #ifndef VAR_H_RAIL_1 #define VAR_H_RAIL_1 class StringVar; class ListVar; class NilVar; class Closure; class Var { public: Var() : refCount(0) {} virtual ~Var() {} void acquire(void) { ++refCount; } void release(void) { --refCount; if (refCount <= 0) { delete this; } } virtual StringVar * getString(void)=0; virtual ListVar * getList(void)=0; virtual NilVar * getNil(void)=0; virtual Closure * getClosure(void)=0; virtual std::string toString(void) const=0; private: Var(Var const &) {} Var & operator=(Var const &) { return *this; } private: int refCount; }; #endif