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#include "type.hpp"
#include <ostream>
#include <sstream>
#include <algorithm>
#include <vector>
#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 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 mgr.substitute(subst, monotype);
}
void type_var::print(const type_mgr& mgr, std::ostream& to) const {
auto type = mgr.lookup(name);
if(type) {
type->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 {
type_var* var;
bool print_parenths = dynamic_cast<type_arr*>(mgr.resolve(left, var).get()) != nullptr;
if(print_parenths) to << "(";
left->print(mgr, to);
if(print_parenths) to << ")";
to << " -> ";
right->print(mgr, to);
}
void type_app::print(const type_mgr& mgr, std::ostream& to) const {
constructor->print(mgr, to);
to << "*";
for(auto& arg : arguments) {
to << " ";
arg->print(mgr, 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::lookup(const std::string& var) const {
auto types_it = types.find(var);
if(types_it != types.end()) return types_it->second;
return nullptr;
}
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, const std::optional<yy::location>& loc) {
type_var *lvar, *rvar;
type_arr *larr, *rarr;
type_base *lid, *rid;
type_app *lapp, *rapp;
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, loc);
unify(larr->right, rarr->right, loc);
return;
} else if((lid = dynamic_cast<type_base*>(l.get())) &&
(rid = dynamic_cast<type_base*>(r.get()))) {
if(lid->name == rid->name &&
lid->arity == rid->arity)
return;
} else if((lapp = dynamic_cast<type_app*>(l.get())) &&
(rapp = dynamic_cast<type_app*>(r.get()))) {
unify(lapp->constructor, rapp->constructor, loc);
auto left_it = lapp->arguments.begin();
auto right_it = rapp->arguments.begin();
while(left_it != lapp->arguments.end() &&
right_it != rapp->arguments.end()) {
unify(*left_it, *right_it, loc);
left_it++, right_it++;
}
return;
}
throw unification_error(l, r, loc);
}
type_ptr type_mgr::substitute(const std::map<std::string, type_ptr>& subst, const type_ptr& t) const {
type_ptr temp = t;
while(type_var* var = dynamic_cast<type_var*>(temp.get())) {
auto subst_it = subst.find(var->name);
if(subst_it != subst.end()) return subst_it->second;
auto var_it = types.find(var->name);
if(var_it == types.end()) return t;
temp = var_it->second;
}
if(type_arr* arr = dynamic_cast<type_arr*>(temp.get())) {
auto left_result = substitute(subst, arr->left);
auto right_result = substitute(subst, arr->right);
if(left_result == arr->left && right_result == arr->right) return t;
return type_ptr(new type_arr(left_result, right_result));
} else if(type_app* app = dynamic_cast<type_app*>(temp.get())) {
auto constructor_result = substitute(subst, app->constructor);
bool arg_changed = false;
std::vector<type_ptr> new_args;
for(auto& arg : app->arguments) {
auto arg_result = substitute(subst, arg);
arg_changed |= arg_result != arg;
new_args.push_back(std::move(arg_result));
}
if(constructor_result == app->constructor && !arg_changed) return t;
type_app* new_app = new type_app(std::move(constructor_result));
std::swap(new_app->arguments, new_args);
return type_ptr(new_app);
}
return t;
}
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);
} else if(type_app* app = dynamic_cast<type_app*>(resolved.get())) {
find_free(app->constructor, into);
for(auto& arg : app->arguments) find_free(arg, into);
}
}
void type_mgr::find_free(const type_scheme_ptr& t, std::set<std::string>& into) const {
std::set<std::string> monotype_free;
type_mgr limited_mgr;
for(auto& binding : types) {
auto existing_position = std::find(t->forall.begin(), t->forall.end(), binding.first);
if(existing_position != t->forall.end()) continue;
limited_mgr.types[binding.first] = binding.second;
}
limited_mgr.find_free(t->monotype, monotype_free);
for(auto& not_free : t->forall) {
monotype_free.erase(not_free);
}
into.insert(monotype_free.begin(), monotype_free.end());
}