160 lines
5.7 KiB
C++
160 lines
5.7 KiB
C++
/** @file Lambda.hpp
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*
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* Author: Roland Conybeare
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**/
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#pragma once
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#include "Expression.hpp"
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#include "FunctionInterface.hpp"
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#include "Variable.hpp"
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#include "LocalEnv.hpp"
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#include <map>
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#include <vector>
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#include <string>
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//#include <cstdint>
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namespace xo {
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namespace ast {
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/** @class Lambda
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* @brief abstract syntax tree for a function definition
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*
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**/
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class Lambda : public FunctionInterface {
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public:
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/**
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* @p name Name for this lambda -- must be unique
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* @p argv Formal parameters, in left-to-right order
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* @p body Expression for body of this function
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**/
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static ref::rp<Lambda> make(const std::string & name,
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const std::vector<ref::rp<Variable>> & argv,
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const ref::rp<Expression> & body);
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/** downcast from Expression **/
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static ref::brw<Lambda> from(ref::brw<Expression> x) {
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return ref::brw<Lambda>::from(x);
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}
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const std::string & type_str() const { return type_str_; }
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const std::vector<ref::rp<Variable>> & argv() const { return local_env_->argv(); }
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const ref::rp<Expression> & body() const { return body_; }
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bool needs_closure_flag() const { return !free_var_set_.empty(); }
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// ----- FunctionInterface -----
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virtual const std::string & name() const override { return name_; }
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/** return number of arguments expected by this function **/
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virtual int n_arg() const override { return local_env_->n_arg(); }
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virtual TypeDescr fn_retval() const override { return body_->valuetype(); }
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virtual TypeDescr fn_arg(uint32_t i) const override { return local_env_->fn_arg(i); }
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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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for (const auto & arg : local_env_->argv())
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n += arg->visit_preorder(visitor_fn);
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n += body_->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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return n;
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}
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virtual ref::rp<Expression> xform_layer(TransformFn /*xform_fn*/) override {
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/* a layer is bounded by lambdas, don't enter them */
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return this;
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}
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virtual void attach_envs(ref::brw<Environment> p) override;
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virtual void display(std::ostream & os) const override;
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private:
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/** @param lambda_type. function type for this lambda.
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* We arbitrarily choose the form "Retval(*)(Args...)"
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**/
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Lambda(const std::string & name,
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TypeDescr lambda_type,
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const ref::rp<LocalEnv> & local_env,
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const ref::rp<Expression> & body);
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/** compute free-variable set for this lambda **/
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std::set<std::string> calc_free_variables() const;
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/** ensure at most one Variable instance with a particular name
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* in this lambda, but ignore nested lambdas.
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*
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* Goal is to unify variables that can use the same binding
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* path to determine memory location at runtime.
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**/
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std::map<std::string, ref::rp<Variable>> regularize_layer_vars();
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private:
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/** lambda name. Initially supporting only form like
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* (define (foo x y z)
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* (+ (* x x) (* y y) (* z z)))
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*
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* In any case need to supply names for distinct things-for-which-code-is-generated
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* so that they can be linked etc.
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**/
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std::string name_;
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/** e.g.
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* "double(double,double)" for function of two doubles that returns a double
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**/
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std::string type_str_;
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/** function body **/
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ref::rp<Expression> body_;
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/** free variables for this lambda **/
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std::set<std::string> free_var_set_;
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/** map giving unique identity to each variable appearing in this layer.
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* includes:
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* - formal parameters
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* - free variables in @ref body_
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* excludes:
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* - any variables appearing in nested lambdas
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* (whether formals or free variables)
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**/
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std::map<std::string, ref::rp<Variable>> layer_var_map_;
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/** all lambdas nested once inside this lambda's body **/
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std::map<std::string, ref::brw<Lambda>> nested_lambda_map_;
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/** established (once) by @ref attach_envs.
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*
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* @note data dependency on ancestor expressions that don't exist yet
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* when Lambda constructor runs, so we need to assign @ref local_env_
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* later.
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**/
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ref::rp<LocalEnv> local_env_;
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}; /*Lambda*/
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inline ref::rp<Lambda>
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make_lambda(const std::string & name,
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const std::vector<ref::rp<Variable>> & argv,
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const ref::rp<Expression> & body)
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{
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return Lambda::make(name, argv, body);
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}
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} /*namespace ast*/
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} /*namespace xo*/
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/** end Lambda.hpp **/
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