A Hugo incarnation of the blog. https://danilafe.com
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
 

148 lines
3.7 KiB

#include "type.hpp"
#include <ostream>
#include <sstream>
#include <algorithm>
#include "error.hpp"
void type_scheme::print(const type_mgr& mgr, std::ostream& to) const {
if(forall.size() != 0) {
to << "forall ";
for(auto& var : forall) {
to << var << " ";
}
to << ". ";
}
monotype->print(mgr, to);
}
type_ptr substitute(const type_mgr& mgr, const std::map<std::string, type_ptr>& subst, const type_ptr& t) {
type_var* var;
type_ptr resolved = mgr.resolve(t, var);
if(var) {
auto subst_it = subst.find(var->name);
if(subst_it == subst.end()) return resolved;
return subst_it->second;
} else if(type_arr* arr = dynamic_cast<type_arr*>(t.get())) {
auto left_result = substitute(mgr, subst, arr->left);
auto right_result = substitute(mgr, subst, arr->right);
if(left_result == arr->left && right_result == arr->right) return t;
return type_ptr(new type_arr(left_result, right_result));
}
return t;
}
type_ptr type_scheme::instantiate(type_mgr& mgr) const {
if(forall.size() == 0) return monotype;
std::map<std::string, type_ptr> subst;
for(auto& var : forall) {
subst[var] = mgr.new_type();
}
return substitute(mgr, subst, monotype);
}
void type_var::print(const type_mgr& mgr, std::ostream& to) const {
auto it = mgr.types.find(name);
if(it != mgr.types.end()) {
it->second->print(mgr, to);
} else {
to << name;
}
}
void type_base::print(const type_mgr& mgr, std::ostream& to) const {
to << name;
}
void type_arr::print(const type_mgr& mgr, std::ostream& to) const {
left->print(mgr, to);
to << " -> (";
right->print(mgr, to);
to << ")";
}
std::string type_mgr::new_type_name() {
int temp = last_id++;
std::string str = "";
while(temp != -1) {
str += (char) ('a' + (temp % 26));
temp = temp / 26 - 1;
}
std::reverse(str.begin(), str.end());
return str;
}
type_ptr type_mgr::new_type() {
return type_ptr(new type_var(new_type_name()));
}
type_ptr type_mgr::new_arrow_type() {
return type_ptr(new type_arr(new_type(), new_type()));
}
type_ptr type_mgr::resolve(type_ptr t, type_var*& var) const {
type_var* cast;
var = nullptr;
while((cast = dynamic_cast<type_var*>(t.get()))) {
auto it = types.find(cast->name);
if(it == types.end()) {
var = cast;
break;
}
t = it->second;
}
return t;
}
void type_mgr::unify(type_ptr l, type_ptr r) {
type_var* lvar;
type_var* rvar;
type_arr* larr;
type_arr* rarr;
type_base* lid;
type_base* rid;
l = resolve(l, lvar);
r = resolve(r, rvar);
if(lvar) {
bind(lvar->name, r);
return;
} else if(rvar) {
bind(rvar->name, l);
return;
} else if((larr = dynamic_cast<type_arr*>(l.get())) &&
(rarr = dynamic_cast<type_arr*>(r.get()))) {
unify(larr->left, rarr->left);
unify(larr->right, rarr->right);
return;
} else if((lid = dynamic_cast<type_base*>(l.get())) &&
(rid = dynamic_cast<type_base*>(r.get()))) {
if(lid->name == rid->name) return;
}
throw unification_error(l, r);
}
void type_mgr::bind(const std::string& s, type_ptr t) {
type_var* other = dynamic_cast<type_var*>(t.get());
if(other && other->name == s) return;
types[s] = t;
}
void type_mgr::find_free(const type_ptr& t, std::set<std::string>& into) const {
type_var* var;
type_ptr resolved = resolve(t, var);
if(var) {
into.insert(var->name);
} else if(type_arr* arr = dynamic_cast<type_arr*>(resolved.get())) {
find_free(arr->left, into);
find_free(arr->right, into);
}
}