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xo-expression: Lambda caches free var set + ::needs_closure() method

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This commit is contained in:
Roland Conybeare 2024-07-01 20:53:22 -04:00
commit 97264b726f
2 changed files with 24 additions and 8 deletions
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16
include/xo/expression/Lambda.hpp
View file

@ -39,6 +39,8 @@ namespace xo {
const std::vector<ref::rp<Variable>> & argv() const { return local_env_->argv(); }
const ref::rp<Expression> & body() const { return body_; }
bool needs_closure_flag() const { return !free_var_set_.empty(); }
// ----- FunctionInterface -----
virtual const std::string & name() const override { return name_; }
@ -50,13 +52,7 @@ namespace xo {
// ----- Expression -----
virtual std::set<std::string> get_free_variables() const override {
std::set<std::string> retval = body_->get_free_variables();
/* but remove formals. */
for (const auto & var : local_env_->argv())
retval.erase(var->name());
return retval;
return this->free_var_set_;
}
virtual std::size_t visit_preorder(VisitFn visitor_fn) override {
@ -87,6 +83,9 @@ namespace xo {
const ref::rp<LocalEnv> & local_env,
const ref::rp<Expression> & body);
/** compute free-variable set for this lambda **/
std::set<std::string> calc_free_variables() const;
private:
/** lambda name. Initially supporting only form like
* (define (foo x y z)
@ -103,6 +102,9 @@ namespace xo {
/** function body **/
ref::rp<Expression> body_;
/** free variables for this lambda **/
std::set<std::string> free_var_set_;
/** established (once) by @ref attach_envs.
*
* @note data dependency on ancestor expressions that don't exist yet

16
src/expression/Lambda.cpp
View file

@ -45,6 +45,19 @@ namespace xo {
body);
} /*make*/
std::set<std::string>
Lambda::calc_free_variables() const
{
std::set<std::string> retval
= body_->get_free_variables();
/* but remove formals. */
for (const auto & var : local_env_->argv())
retval.erase(var->name());
return retval;
} /*calc_free_variables*/
Lambda::Lambda(const std::string & name,
TypeDescr lambda_type,
const rp<LocalEnv> & local_env,
@ -64,7 +77,8 @@ namespace xo {
}
ss << ")";
type_str_ = ss.str();
this->type_str_ = ss.str();
this->free_var_set_ = this->calc_free_variables();
body_->attach_envs(local_env_);
} /*ctor*/