131 lines
3.8 KiB
C++
131 lines
3.8 KiB
C++
/* file DefineExpr.hpp
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*
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* author: Roland Conybeare, Jul 2024
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*/
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#pragma once
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#include "Expression.hpp"
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namespace xo {
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namespace ast {
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/** @class DefineExpr
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* @brief Provide definition for a constant, variable or function
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*
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* At toplevel, introduces a new global variable.
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* In a nested context,
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*
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* def foo = rhsexpr
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* body...
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*
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* is equivalent to
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*
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* (lambda (foo) body...)(rhsexpr)
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*
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* Promise:
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* - memory location of @ref lhs_var_ is determined when parent DefineExpr
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* constructed, and is stable across calls to @ref DefineExpr::assign_lhs_name
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**/
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class DefineExpr : public Expression {
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public:
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static rp<DefineExpr> make(std::string name,
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rp<Expression> value);
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static bp<DefineExpr> from(bp<Expression> x) {
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return bp<DefineExpr>::from(x);
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}
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const std::string & lhs_name() const;
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const rp<Expression> & rhs() const { return rhs_; }
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const rp<Variable>& lhs_variable() const { return lhs_var_; }
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std::set<std::string> calc_free_variables() const;
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// ----- Expression -----
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virtual std::set<std::string> get_free_variables() const override {
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return this->free_var_set_;
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}
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virtual std::size_t visit_preorder(VisitFn visitor_fn) override {
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std::size_t n = 1;
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visitor_fn(this);
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n += rhs_->visit_preorder(visitor_fn);
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return n;
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}
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virtual std::size_t visit_layer(VisitFn visitor_fn) override {
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std::size_t n = 1;
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visitor_fn(this);
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n += this->rhs_->visit_layer(visitor_fn);
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return n;
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}
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virtual rp<Expression> xform_layer(TransformFn xform_fn) override {
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this->rhs_ = this->rhs_->xform_layer(xform_fn);
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return xform_fn(this);
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}
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virtual void attach_envs(bp<Environment> p) override {
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rhs_->attach_envs(p);
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}
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virtual void display(std::ostream & os) const override;
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virtual std::uint32_t pretty_print(const ppindentinfo & ppii) const override;
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protected:
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/**
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*
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**/
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DefineExpr(TypeDescr rhs_valuetype,
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std::string lhs_name,
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rp<Expression> rhs);
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protected:
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/** symbol name for this definition **/
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rp<Variable> lhs_var_;
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/** right-hand side of definition **/
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rp<Expression> rhs_;
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/** free variables for this definition **/
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std::set<std::string> free_var_set_;
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};
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/** @class DefineExprAccess
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* @brief DefineExpr with writeable members.
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*
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* Convenient when scaffolding a parser,
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* e.g. see xo-parser
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**/
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class DefineExprAccess : public DefineExpr {
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public:
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static rp<DefineExprAccess> make(std::string lhs_name,
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rp<Expression> rhs);
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static rp<DefineExprAccess> make_empty();
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void assign_lhs_name(const std::string & x);
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void assign_rhs(const rp<Expression> & x);
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private:
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DefineExprAccess(TypeDescr rhs_valuetype,
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std::string lhs_name,
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rp<Expression> rhs)
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: DefineExpr(rhs_valuetype,
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std::move(lhs_name),
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std::move(rhs))
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{}
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};
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} /*namespace ast*/
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} /*namespace xo*/
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/* end DefineExpr.hpp */
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