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23 changed files with 5 additions and 1020 deletions

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cmake_minimum_required(VERSION 3.1)
project(compiler)
find_package(BISON)
find_package(FLEX)
bison_target(parser
${CMAKE_CURRENT_SOURCE_DIR}/parser.y
${CMAKE_CURRENT_BINARY_DIR}/parser.cpp
COMPILE_FLAGS "-d")
flex_target(scanner
${CMAKE_CURRENT_SOURCE_DIR}/scanner.l
${CMAKE_CURRENT_BINARY_DIR}/scanner.cpp)
add_flex_bison_dependency(scanner parser)
add_executable(compiler
ast.cpp ast.hpp definition.cpp
type_env.cpp type_env.hpp
env.cpp env.hpp
type.cpp type.hpp
error.cpp error.hpp
${BISON_parser_OUTPUTS}
${FLEX_scanner_OUTPUTS}
main.cpp
)
target_include_directories(compiler PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
target_include_directories(compiler PUBLIC ${CMAKE_CURRENT_BINARY_DIR})

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@ -1,144 +0,0 @@
#include "ast.hpp"
#include <ostream>
#include "error.hpp"
std::string op_name(binop op) {
switch(op) {
case PLUS: return "+";
case MINUS: return "-";
case TIMES: return "*";
case DIVIDE: return "/";
}
return "??";
}
void print_indent(int n, std::ostream& to) {
while(n--) to << " ";
}
void ast_int::print(int indent, std::ostream& to) const {
print_indent(indent, to);
to << "INT: " << value << std::endl;
}
type_ptr ast_int::typecheck(type_mgr& mgr, const type_env& env) const {
return type_ptr(new type_base("Int"));
}
void ast_lid::print(int indent, std::ostream& to) const {
print_indent(indent, to);
to << "LID: " << id << std::endl;
}
type_ptr ast_lid::typecheck(type_mgr& mgr, const type_env& env) const {
return env.lookup(id);
}
void ast_uid::print(int indent, std::ostream& to) const {
print_indent(indent, to);
to << "UID: " << id << std::endl;
}
type_ptr ast_uid::typecheck(type_mgr& mgr, const type_env& env) const {
return env.lookup(id);
}
void ast_binop::print(int indent, std::ostream& to) const {
print_indent(indent, to);
to << "BINOP: " << op_name(op) << std::endl;
left->print(indent + 1, to);
right->print(indent + 1, to);
}
type_ptr ast_binop::typecheck(type_mgr& mgr, const type_env& env) const {
type_ptr ltype = left->typecheck(mgr, env);
type_ptr rtype = right->typecheck(mgr, env);
type_ptr ftype = env.lookup(op_name(op));
if(!ftype) throw type_error(std::string("unknown binary operator ") + op_name(op));
type_ptr return_type = mgr.new_type();
type_ptr arrow_one = type_ptr(new type_arr(rtype, return_type));
type_ptr arrow_two = type_ptr(new type_arr(ltype, arrow_one));
mgr.unify(arrow_two, ftype);
return return_type;
}
void ast_app::print(int indent, std::ostream& to) const {
print_indent(indent, to);
to << "APP:" << std::endl;
left->print(indent + 1, to);
right->print(indent + 1, to);
}
type_ptr ast_app::typecheck(type_mgr& mgr, const type_env& env) const {
type_ptr ltype = left->typecheck(mgr, env);
type_ptr rtype = right->typecheck(mgr, env);
type_ptr return_type = mgr.new_type();
type_ptr arrow = type_ptr(new type_arr(rtype, return_type));
mgr.unify(arrow, ltype);
return return_type;
}
void ast_case::print(int indent, std::ostream& to) const {
print_indent(indent, to);
to << "CASE: " << std::endl;
for(auto& branch : branches) {
print_indent(indent + 1, to);
branch->pat->print(to);
to << std::endl;
branch->expr->print(indent + 2, to);
}
}
type_ptr ast_case::typecheck(type_mgr& mgr, const type_env& env) const {
type_var* var;
type_ptr case_type = mgr.resolve(of->typecheck(mgr, env), var);
type_ptr branch_type = mgr.new_type();
if(!dynamic_cast<type_base*>(case_type.get())) {
throw type_error("attempting case analysis of non-data type");
}
for(auto& branch : branches) {
type_env new_env = env.scope();
branch->pat->match(case_type, mgr, new_env);
type_ptr curr_branch_type = branch->expr->typecheck(mgr, new_env);
mgr.unify(branch_type, curr_branch_type);
}
return branch_type;
}
void pattern_var::print(std::ostream& to) const {
to << var;
}
void pattern_var::match(type_ptr t, type_mgr& mgr, type_env& env) const {
env.bind(var, t);
}
void pattern_constr::print(std::ostream& to) const {
to << constr;
for(auto& param : params) {
to << " " << param;
}
}
void pattern_constr::match(type_ptr t, type_mgr& mgr, type_env& env) const {
type_ptr constructor_type = env.lookup(constr);
if(!constructor_type) {
throw type_error(std::string("pattern using unknown constructor ") + constr);
}
for(int i = 0; i < params.size(); i++) {
type_arr* arr = dynamic_cast<type_arr*>(constructor_type.get());
if(!arr) throw type_error("too many parameters in constructor pattern");
env.bind(params[i], arr->left);
constructor_type = arr->right;
}
mgr.unify(t, constructor_type);
}

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@ -1,170 +0,0 @@
#pragma once
#include <memory>
#include <vector>
#include "type.hpp"
#include "type_env.hpp"
#include "binop.hpp"
#include "instruction.hpp"
#include "env.hpp"
struct ast {
virtual ~ast() = default;
virtual void print(int indent, std::ostream& to) const = 0;
virtual type_ptr typecheck(type_mgr& mgr, const type_env& env) const = 0;
virtual void compile(const env_ptr env,
std::vector<instruction>& into) const;
};
using ast_ptr = std::unique_ptr<ast>;
struct pattern {
virtual ~pattern() = default;
virtual void print(std::ostream& to) const = 0;
virtual void match(type_ptr t, type_mgr& mgr, type_env& env) const = 0;
};
using pattern_ptr = std::unique_ptr<pattern>;
struct branch {
pattern_ptr pat;
ast_ptr expr;
branch(pattern_ptr p, ast_ptr a)
: pat(std::move(p)), expr(std::move(a)) {}
};
using branch_ptr = std::unique_ptr<branch>;
struct constructor {
std::string name;
std::vector<std::string> types;
constructor(std::string n, std::vector<std::string> ts)
: name(std::move(n)), types(std::move(ts)) {}
};
using constructor_ptr = std::unique_ptr<constructor>;
struct definition {
virtual ~definition() = default;
virtual void typecheck_first(type_mgr& mgr, type_env& env) = 0;
virtual void typecheck_second(type_mgr& mgr, const type_env& env) const = 0;
};
using definition_ptr = std::unique_ptr<definition>;
struct ast_int : public ast {
int value;
explicit ast_int(int v)
: value(v) {}
void print(int indent, std::ostream& to) const;
type_ptr typecheck(type_mgr& mgr, const type_env& env) const;
};
struct ast_lid : public ast {
std::string id;
explicit ast_lid(std::string i)
: id(std::move(i)) {}
void print(int indent, std::ostream& to) const;
type_ptr typecheck(type_mgr& mgr, const type_env& env) const;
};
struct ast_uid : public ast {
std::string id;
explicit ast_uid(std::string i)
: id(std::move(i)) {}
void print(int indent, std::ostream& to) const;
type_ptr typecheck(type_mgr& mgr, const type_env& env) const;
};
struct ast_binop : public ast {
binop op;
ast_ptr left;
ast_ptr right;
ast_binop(binop o, ast_ptr l, ast_ptr r)
: op(o), left(std::move(l)), right(std::move(r)) {}
void print(int indent, std::ostream& to) const;
type_ptr typecheck(type_mgr& mgr, const type_env& env) const;
};
struct ast_app : public ast {
ast_ptr left;
ast_ptr right;
ast_app(ast_ptr l, ast_ptr r)
: left(std::move(l)), right(std::move(r)) {}
void print(int indent, std::ostream& to) const;
type_ptr typecheck(type_mgr& mgr, const type_env& env) const;
};
struct ast_case : public ast {
ast_ptr of;
std::vector<branch_ptr> branches;
ast_case(ast_ptr o, std::vector<branch_ptr> b)
: of(std::move(o)), branches(std::move(b)) {}
void print(int indent, std::ostream& to) const;
type_ptr typecheck(type_mgr& mgr, const type_env& env) const;
};
struct pattern_var : public pattern {
std::string var;
pattern_var(std::string v)
: var(std::move(v)) {}
void print(std::ostream &to) const;
void match(type_ptr t, type_mgr& mgr, type_env& env) const;
};
struct pattern_constr : public pattern {
std::string constr;
std::vector<std::string> params;
pattern_constr(std::string c, std::vector<std::string> p)
: constr(std::move(c)), params(std::move(p)) {}
void print(std::ostream &to) const;
void match(type_ptr t, type_mgr&, type_env& env) const;
};
struct definition_defn : public definition {
std::string name;
std::vector<std::string> params;
ast_ptr body;
type_ptr return_type;
std::vector<type_ptr> param_types;
definition_defn(std::string n, std::vector<std::string> p, ast_ptr b)
: name(std::move(n)), params(std::move(p)), body(std::move(b)) {
}
void typecheck_first(type_mgr& mgr, type_env& env);
void typecheck_second(type_mgr& mgr, const type_env& env) const;
};
struct definition_data : public definition {
std::string name;
std::vector<constructor_ptr> constructors;
definition_data(std::string n, std::vector<constructor_ptr> cs)
: name(std::move(n)), constructors(std::move(cs)) {}
void typecheck_first(type_mgr& mgr, type_env& env);
void typecheck_second(type_mgr& mgr, const type_env& env) const;
};

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#pragma once
enum binop {
PLUS,
MINUS,
TIMES,
DIVIDE
};

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#include "ast.hpp"
void definition_defn::typecheck_first(type_mgr& mgr, type_env& env) {
return_type = mgr.new_type();
type_ptr full_type = return_type;
for(auto it = params.rbegin(); it != params.rend(); it++) {
type_ptr param_type = mgr.new_type();
full_type = type_ptr(new type_arr(param_type, full_type));
param_types.push_back(param_type);
}
env.bind(name, full_type);
}
void definition_defn::typecheck_second(type_mgr& mgr, const type_env& env) const {
type_env new_env = env.scope();
auto param_it = params.begin();
auto type_it = param_types.rbegin();
while(param_it != params.end() && type_it != param_types.rend()) {
new_env.bind(*param_it, *type_it);
param_it++;
type_it++;
}
type_ptr body_type = body->typecheck(mgr, new_env);
mgr.unify(return_type, body_type);
}
void definition_data::typecheck_first(type_mgr& mgr, type_env& env) {
type_ptr return_type = type_ptr(new type_base(name));
for(auto& constructor : constructors) {
type_ptr full_type = return_type;
for(auto it = constructor->types.rbegin(); it != constructor->types.rend(); it++) {
type_ptr type = type_ptr(new type_base(*it));
full_type = type_ptr(new type_arr(type, full_type));
}
env.bind(constructor->name, full_type);
}
}
void definition_data::typecheck_second(type_mgr& mgr, const type_env& env) const {
// Nothing
}

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#pragma once
#include <memory>
#include <string>
struct env {
virtual ~env() = default;
virtual int get_offset(const std::string& name) const = 0;
};
using env_ptr = std::shared_ptr<env>;
struct env_var {
std::string name;
env_ptr parent;
env_var(std::string& n, env_ptr p)
: name(std::move(n)), parent(std::move(p)) {}
virtual int get_offset(const std::string& name) const;
};
struct env_offset {
int offset;
env_ptr parent;
env_offset(int o, env_ptr p)
: offset(o), parent(std::move(p)) {}
virtual int get_offset(const std::string& name) const;
};

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#include "error.hpp"
const char* type_error::what() const noexcept {
return "an error occured while checking the types of the program";
}

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#pragma once
#include <exception>
#include "type.hpp"
struct type_error : std::exception {
std::string description;
type_error(std::string d)
: description(std::move(d)) {}
const char* what() const noexcept override;
};
struct unification_error : public type_error {
type_ptr left;
type_ptr right;
unification_error(type_ptr l, type_ptr r)
: left(std::move(l)), right(std::move(r)),
type_error("failed to unify types") {}
};

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data Bool = { True, False }
defn main = { 3 + True }

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defn main = { 1 2 3 4 5 }

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data List = { Nil, Cons Int List }
defn head l = {
case l of {
Nil -> { 0 }
Cons x y z -> { x }
}
}

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defn main = { plus 320 6 }
defn plus x y = { x + y }

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defn add x y = { x + y }
defn double x = { add x x }
defn main = { double 163 }

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data List = { Nil, Cons Int List }
defn length l = {
case l of {
Nil -> { 0 }
Cons x xs -> { 1 + length xs }
}
}

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#pragma once
#include <string>
#include <memory>
#include "binop.hpp"
struct instruction {
virtual ~instruction() = default;
};
using instruction_ptr = std::unique_ptr<instruction>;
struct instruction_pushint : public instruction {
int value;
instruction_pushint(int v)
: value(v) {}
};
struct instruction_pushglobal : public instruction {
std::string name;
instruction_pushglobal(std::string n)
: name(std::move(n)) {}
};
struct instruction_push : public instruction {
int offset;
instruction_push(int o)
: offset(o) {}
};
struct instruction_mkapp : public instruction {
};
struct instruction_update : public instruction {
int offset;
instruction_update(int o)
: offset(o) {}
};
struct instruction_pack : public instruction {
int tag;
int size;
instruction_pack(int t, int s)
: tag(t), size(s) {}
};
struct instruction_split : public instruction {
};
struct instruction_slide : public instruction {
int offset;
instruction_slide(int o)
: offset(o) {}
};
struct instruction_binop : public instruction {
binop op;
instruction_binop(binop o)
: op(o) {}
};
struct instruction_eval : public instruction {
};
struct instruction_alloc : public instruction {
int amount;
instruction_alloc(int a)
: amount(a) {}
};
struct instruction_unwind : public instruction {
};

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#include "ast.hpp"
#include <iostream>
#include "parser.hpp"
#include "error.hpp"
#include "type.hpp"
void yy::parser::error(const std::string& msg) {
std::cout << "An error occured: " << msg << std::endl;
}
extern std::vector<definition_ptr> program;
void typecheck_program(
const std::vector<definition_ptr>& prog,
type_mgr& mgr, type_env& env) {
type_ptr int_type = type_ptr(new type_base("Int"));
type_ptr binop_type = type_ptr(new type_arr(
int_type,
type_ptr(new type_arr(int_type, int_type))));
env.bind("+", binop_type);
env.bind("-", binop_type);
env.bind("*", binop_type);
env.bind("/", binop_type);
for(auto& def : prog) {
def->typecheck_first(mgr, env);
}
for(auto& def : prog) {
def->typecheck_second(mgr, env);
}
for(auto& pair : env.names) {
std::cout << pair.first << ": ";
pair.second->print(mgr, std::cout);
std::cout << std::endl;
}
}
int main() {
yy::parser parser;
type_mgr mgr;
type_env env;
parser.parse();
for(auto& definition : program) {
definition_defn* def = dynamic_cast<definition_defn*>(definition.get());
if(!def) continue;
std::cout << def->name;
for(auto& param : def->params) std::cout << " " << param;
std::cout << ":" << std::endl;
def->body->print(1, std::cout);
}
try {
typecheck_program(program, mgr, env);
} catch(unification_error& err) {
std::cout << "failed to unify types: " << std::endl;
std::cout << " (1) \033[34m";
err.left->print(mgr, std::cout);
std::cout << "\033[0m" << std::endl;
std::cout << " (2) \033[32m";
err.right->print(mgr, std::cout);
std::cout << "\033[0m" << std::endl;
} catch(type_error& err) {
std::cout << "failed to type check program: " << err.description << std::endl;
}
}

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%{
#include <string>
#include <iostream>
#include "ast.hpp"
#include "parser.hpp"
std::vector<definition_ptr> program;
extern yy::parser::symbol_type yylex();
%}
%token PLUS
%token TIMES
%token MINUS
%token DIVIDE
%token <int> INT
%token DEFN
%token DATA
%token CASE
%token OF
%token OCURLY
%token CCURLY
%token OPAREN
%token CPAREN
%token COMMA
%token ARROW
%token EQUAL
%token <std::string> LID
%token <std::string> UID
%language "c++"
%define api.value.type variant
%define api.token.constructor
%type <std::vector<std::string>> lowercaseParams uppercaseParams
%type <std::vector<definition_ptr>> program definitions
%type <std::vector<branch_ptr>> branches
%type <std::vector<constructor_ptr>> constructors
%type <ast_ptr> aAdd aMul case app appBase
%type <definition_ptr> definition defn data
%type <branch_ptr> branch
%type <pattern_ptr> pattern
%type <constructor_ptr> constructor
%start program
%%
program
: definitions { program = std::move($1); }
;
definitions
: definitions definition { $$ = std::move($1); $$.push_back(std::move($2)); }
| definition { $$ = std::vector<definition_ptr>(); $$.push_back(std::move($1)); }
;
definition
: defn { $$ = std::move($1); }
| data { $$ = std::move($1); }
;
defn
: DEFN LID lowercaseParams EQUAL OCURLY aAdd CCURLY
{ $$ = definition_ptr(
new definition_defn(std::move($2), std::move($3), std::move($6))); }
;
lowercaseParams
: %empty { $$ = std::vector<std::string>(); }
| lowercaseParams LID { $$ = std::move($1); $$.push_back(std::move($2)); }
;
uppercaseParams
: %empty { $$ = std::vector<std::string>(); }
| uppercaseParams UID { $$ = std::move($1); $$.push_back(std::move($2)); }
;
aAdd
: aAdd PLUS aMul { $$ = ast_ptr(new ast_binop(PLUS, std::move($1), std::move($3))); }
| aAdd MINUS aMul { $$ = ast_ptr(new ast_binop(MINUS, std::move($1), std::move($3))); }
| aMul { $$ = std::move($1); }
;
aMul
: aMul TIMES app { $$ = ast_ptr(new ast_binop(TIMES, std::move($1), std::move($3))); }
| aMul DIVIDE app { $$ = ast_ptr(new ast_binop(DIVIDE, std::move($1), std::move($3))); }
| app { $$ = std::move($1); }
;
app
: app appBase { $$ = ast_ptr(new ast_app(std::move($1), std::move($2))); }
| appBase { $$ = std::move($1); }
;
appBase
: INT { $$ = ast_ptr(new ast_int($1)); }
| LID { $$ = ast_ptr(new ast_lid(std::move($1))); }
| UID { $$ = ast_ptr(new ast_uid(std::move($1))); }
| OPAREN aAdd CPAREN { $$ = std::move($2); }
| case { $$ = std::move($1); }
;
case
: CASE aAdd OF OCURLY branches CCURLY
{ $$ = ast_ptr(new ast_case(std::move($2), std::move($5))); }
;
branches
: branches branch { $$ = std::move($1); $$.push_back(std::move($2)); }
| branch { $$ = std::vector<branch_ptr>(); $$.push_back(std::move($1));}
;
branch
: pattern ARROW OCURLY aAdd CCURLY
{ $$ = branch_ptr(new branch(std::move($1), std::move($4))); }
;
pattern
: LID { $$ = pattern_ptr(new pattern_var(std::move($1))); }
| UID lowercaseParams
{ $$ = pattern_ptr(new pattern_constr(std::move($1), std::move($2))); }
;
data
: DATA UID EQUAL OCURLY constructors CCURLY
{ $$ = definition_ptr(new definition_data(std::move($2), std::move($5))); }
;
constructors
: constructors COMMA constructor { $$ = std::move($1); $$.push_back(std::move($3)); }
| constructor
{ $$ = std::vector<constructor_ptr>(); $$.push_back(std::move($1)); }
;
constructor
: UID uppercaseParams
{ $$ = constructor_ptr(new constructor(std::move($1), std::move($2))); }
;

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%option noyywrap
%{
#include <iostream>
#include "ast.hpp"
#include "parser.hpp"
#define YY_DECL yy::parser::symbol_type yylex()
%}
%%
[ \n]+ {}
\+ { return yy::parser::make_PLUS(); }
\* { return yy::parser::make_TIMES(); }
- { return yy::parser::make_MINUS(); }
\/ { return yy::parser::make_DIVIDE(); }
[0-9]+ { return yy::parser::make_INT(atoi(yytext)); }
defn { return yy::parser::make_DEFN(); }
data { return yy::parser::make_DATA(); }
case { return yy::parser::make_CASE(); }
of { return yy::parser::make_OF(); }
\{ { return yy::parser::make_OCURLY(); }
\} { return yy::parser::make_CCURLY(); }
\( { return yy::parser::make_OPAREN(); }
\) { return yy::parser::make_CPAREN(); }
, { return yy::parser::make_COMMA(); }
-> { return yy::parser::make_ARROW(); }
= { return yy::parser::make_EQUAL(); }
[a-z][a-zA-Z]* { return yy::parser::make_LID(std::string(yytext)); }
[A-Z][a-zA-Z]* { return yy::parser::make_UID(std::string(yytext)); }
%%

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#include "type.hpp"
#include <sstream>
#include <algorithm>
#include "error.hpp"
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) {
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;
}

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@ -1,54 +0,0 @@
#pragma once
#include <memory>
#include <map>
struct type_mgr;
struct type {
virtual ~type() = default;
virtual void print(const type_mgr& mgr, std::ostream& to) const = 0;
};
using type_ptr = std::shared_ptr<type>;
struct type_var : public type {
std::string name;
type_var(std::string n)
: name(std::move(n)) {}
void print(const type_mgr& mgr, std::ostream& to) const;
};
struct type_base : public type {
std::string name;
type_base(std::string n)
: name(std::move(n)) {}
void print(const type_mgr& mgr, std::ostream& to) const;
};
struct type_arr : public type {
type_ptr left;
type_ptr right;
type_arr(type_ptr l, type_ptr r)
: left(std::move(l)), right(std::move(r)) {}
void print(const type_mgr& mgr, std::ostream& to) const;
};
struct type_mgr {
int last_id = 0;
std::map<std::string, type_ptr> types;
std::string new_type_name();
type_ptr new_type();
type_ptr new_arrow_type();
void unify(type_ptr l, type_ptr r);
type_ptr resolve(type_ptr t, type_var*& var);
void bind(const std::string& s, type_ptr t);
};

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@ -1,16 +0,0 @@
#include "type_env.hpp"
type_ptr type_env::lookup(const std::string& name) const {
auto it = names.find(name);
if(it != names.end()) return it->second;
if(parent) return parent->lookup(name);
return nullptr;
}
void type_env::bind(const std::string& name, type_ptr t) {
names[name] = t;
}
type_env type_env::scope() const {
return type_env(this);
}

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@ -1,16 +0,0 @@
#pragma once
#include <map>
#include "type.hpp"
struct type_env {
std::map<std::string, type_ptr> names;
type_env const* parent = nullptr;
type_env(type_env const* p)
: parent(p) {}
type_env() : type_env(nullptr) {}
type_ptr lookup(const std::string& name) const;
void bind(const std::string& name, type_ptr t);
type_env scope() const;
};

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@ -161,35 +161,9 @@ graphs when we have to instantiate those functions, we simply
evaluate the arguments and perform the relevant arithmetic operation using BinOp. evaluate the arguments and perform the relevant arithmetic operation using BinOp.
We will do a similar thing for constructors. We will do a similar thing for constructors.
### Implementation With that out of the way, we can get around to writing some code. We can envision
a method on the `ast` struct that takes an environment (just like our compilation
With that out of the way, we can get around to writing some code. Let's scheme takes the environment \\(\\rho\\\)). Rather than returning a vector
first define C++ structs for the instructions of the G-machine:
{{< codeblock "C++" "compiler/06/instruction.hpp" >}}
We can now envision a method on the `ast` struct that takes an environment
(just like our compilation scheme takes the environment \\(\\rho\\\)),
and compiles the `ast`. Rather than returning a vector
of instructions (which involves copying, unless we get some optimization kicking in), of instructions (which involves copying, unless we get some optimization kicking in),
we'll pass a reference to a vector to our method. The method will then place the generated we'll pass to it a reference to a vector. The method will then place the generated
instructions into the vector. instructions into the vector.
There's one more thing to be considered. How do we tell apart a "global"
from a variable? A naive solution would be to take a list or map of
global functions as a third parameter to our `compile` method.
But there's an easier way! We know that the program passed type checking.
This means that every referenced variable exists. From then, the situation is easy -
if actual variable names are kept in the environment, \\(\\rho\\), then whenever
we see a variable that __isn't__ in the current environment, it must be a function name.
Having finished contemplating out method, it's time to define a signature:
```C++
virtual void compile(const env_ptr env, std::vector<instruction>& into) const;
```
Ah, but now we have to define "environment". Let's do that:
{{< codeblock "C++" "compiler/06/env.hpp" >}}
And now, we begin our implementation.