220 lines
6.4 KiB
C++
220 lines
6.4 KiB
C++
#include "type.hpp"
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#include <ostream>
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#include <sstream>
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#include <algorithm>
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#include <vector>
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#include "error.hpp"
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bool type::is_arrow(const type_mgr& mgr) const { return false; }
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void type_scheme::print(const type_mgr& mgr, std::ostream& to) const {
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if(forall.size() != 0) {
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to << "forall ";
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for(auto& var : forall) {
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to << var << " ";
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}
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to << ". ";
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}
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monotype->print(mgr, to);
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}
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type_ptr type_scheme::instantiate(type_mgr& mgr) const {
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if(forall.size() == 0) return monotype;
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std::map<std::string, type_ptr> subst;
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for(auto& var : forall) {
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subst[var] = mgr.new_type();
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}
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return mgr.substitute(subst, monotype);
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}
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void type_var::print(const type_mgr& mgr, std::ostream& to) const {
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auto it = mgr.types.find(name);
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if(it != mgr.types.end()) {
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it->second->print(mgr, to);
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} else {
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to << name;
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}
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}
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bool type_var::is_arrow(const type_mgr& mgr) const {
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auto it = mgr.types.find(name);
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if(it != mgr.types.end()) {
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return it->second->is_arrow(mgr);
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} else {
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return false;
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}
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}
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void type_base::print(const type_mgr& mgr, std::ostream& to) const {
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to << name;
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}
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void type_arr::print(const type_mgr& mgr, std::ostream& to) const {
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bool print_parenths = left->is_arrow(mgr);
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if(print_parenths) to << "(";
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left->print(mgr, to);
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if(print_parenths) to << ")";
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to << " -> ";
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right->print(mgr, to);
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}
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bool type_arr::is_arrow(const type_mgr& mgr) const {
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return true;
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}
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void type_app::print(const type_mgr& mgr, std::ostream& to) const {
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constructor->print(mgr, to);
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to << "*";
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for(auto& arg : arguments) {
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to << " ";
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arg->print(mgr, to);
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}
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}
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std::string type_mgr::new_type_name() {
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int temp = last_id++;
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std::string str = "";
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while(temp != -1) {
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str += (char) ('a' + (temp % 26));
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temp = temp / 26 - 1;
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}
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std::reverse(str.begin(), str.end());
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return str;
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}
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type_ptr type_mgr::new_type() {
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return type_ptr(new type_var(new_type_name()));
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}
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type_ptr type_mgr::new_arrow_type() {
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return type_ptr(new type_arr(new_type(), new_type()));
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}
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type_ptr type_mgr::resolve(type_ptr t, type_var*& var) const {
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type_var* cast;
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var = nullptr;
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while((cast = dynamic_cast<type_var*>(t.get()))) {
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auto it = types.find(cast->name);
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if(it == types.end()) {
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var = cast;
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break;
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}
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t = it->second;
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}
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return t;
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}
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void type_mgr::unify(type_ptr l, type_ptr r, const std::optional<yy::location>& loc) {
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type_var *lvar, *rvar;
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type_arr *larr, *rarr;
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type_base *lid, *rid;
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type_app *lapp, *rapp;
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l = resolve(l, lvar);
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r = resolve(r, rvar);
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if(lvar) {
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bind(lvar->name, r);
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return;
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} else if(rvar) {
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bind(rvar->name, l);
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return;
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} else if((larr = dynamic_cast<type_arr*>(l.get())) &&
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(rarr = dynamic_cast<type_arr*>(r.get()))) {
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unify(larr->left, rarr->left, loc);
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unify(larr->right, rarr->right, loc);
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return;
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} else if((lid = dynamic_cast<type_base*>(l.get())) &&
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(rid = dynamic_cast<type_base*>(r.get()))) {
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if(lid->name == rid->name && lid->arity == rid->arity) return;
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} else if((lapp = dynamic_cast<type_app*>(l.get())) &&
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(rapp = dynamic_cast<type_app*>(r.get()))) {
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unify(lapp->constructor, rapp->constructor, loc);
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auto left_it = lapp->arguments.begin();
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auto right_it = rapp->arguments.begin();
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while(left_it != lapp->arguments.end() &&
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right_it != rapp->arguments.end()) {
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unify(*left_it, *right_it, loc);
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left_it++, right_it++;
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}
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return;
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}
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throw unification_error(l, r, loc);
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}
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type_ptr type_mgr::substitute(const std::map<std::string, type_ptr>& subst, const type_ptr& t) const {
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type_ptr temp = t;
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while(type_var* var = dynamic_cast<type_var*>(temp.get())) {
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auto subst_it = subst.find(var->name);
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if(subst_it != subst.end()) return subst_it->second;
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auto var_it = types.find(var->name);
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if(var_it == types.end()) return t;
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temp = var_it->second;
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}
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if(type_arr* arr = dynamic_cast<type_arr*>(temp.get())) {
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auto left_result = substitute(subst, arr->left);
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auto right_result = substitute(subst, arr->right);
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if(left_result == arr->left && right_result == arr->right) return t;
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return type_ptr(new type_arr(left_result, right_result));
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} else if(type_app* app = dynamic_cast<type_app*>(temp.get())) {
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auto constructor_result = substitute(subst, app->constructor);
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bool arg_changed = false;
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std::vector<type_ptr> new_args;
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for(auto& arg : app->arguments) {
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auto arg_result = substitute(subst, arg);
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arg_changed |= arg_result != arg;
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new_args.push_back(std::move(arg_result));
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}
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if(constructor_result == app->constructor && !arg_changed) return t;
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type_app* new_app = new type_app(std::move(constructor_result));
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std::swap(new_app->arguments, new_args);
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return type_ptr(new_app);
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}
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return t;
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}
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void type_mgr::bind(const std::string& s, type_ptr t) {
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type_var* other = dynamic_cast<type_var*>(t.get());
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if(other && other->name == s) return;
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types[s] = t;
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}
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void type_mgr::find_free(const type_ptr& t, std::set<std::string>& into) const {
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type_var* var;
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type_ptr resolved = resolve(t, var);
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if(var) {
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into.insert(var->name);
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} else if(type_arr* arr = dynamic_cast<type_arr*>(resolved.get())) {
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find_free(arr->left, into);
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find_free(arr->right, into);
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} else if(type_app* app = dynamic_cast<type_app*>(resolved.get())) {
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find_free(app->constructor, into);
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for(auto& arg : app->arguments) find_free(arg, into);
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}
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}
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void type_mgr::find_free(const type_scheme_ptr& t, std::set<std::string>& into) const {
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std::set<std::string> monotype_free;
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type_mgr limited_mgr;
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for(auto& binding : types) {
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auto existing_position = std::find(t->forall.begin(), t->forall.end(), binding.first);
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if(existing_position != t->forall.end()) continue;
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limited_mgr.types[binding.first] = binding.second;
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}
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limited_mgr.find_free(t->monotype, monotype_free);
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for(auto& not_free : t->forall) {
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monotype_free.erase(not_free);
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}
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into.insert(monotype_free.begin(), monotype_free.end());
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}
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