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23 changed files with 1020 additions and 5 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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code/compiler/06/ast.cpp Normal file
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#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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code/compiler/06/ast.hpp Normal file
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#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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code/compiler/06/env.hpp Normal file
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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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code/compiler/06/main.cpp Normal file
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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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code/compiler/06/parser.y Normal file
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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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code/compiler/06/type.cpp Normal file
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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;
}

54
code/compiler/06/type.hpp Normal file
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@ -0,0 +1,54 @@
#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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@ -0,0 +1,16 @@
#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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@ -0,0 +1,16 @@
#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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@ -161,9 +161,35 @@ graphs when we have to instantiate those functions, we simply
evaluate the arguments and perform the relevant arithmetic operation using BinOp.
We will do a similar thing for constructors.
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
scheme takes the environment \\(\\rho\\\)). Rather than returning a vector
### Implementation
With that out of the way, we can get around to writing some code. Let's
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),
we'll pass to it a reference to a vector. The method will then place the generated
instructions into the vector.
we'll pass a reference to a vector to our method. The method will then place the generated
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.