From ad1946e9fbc81cd755a2e1ff9681d997d1e14fff Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Sun, 14 Jun 2020 02:00:20 -0700
Subject: [PATCH] Add first draft of lambdas.

---
 code/compiler/12/ast.cpp   | 64 ++++++++++++++++++++++++++++++++++++++
 code/compiler/12/ast.hpp   | 19 +++++++++++
 code/compiler/12/parser.y  |  9 +++++-
 code/compiler/12/scanner.l |  1 +
 4 files changed, 92 insertions(+), 1 deletion(-)

diff --git a/code/compiler/12/ast.cpp b/code/compiler/12/ast.cpp
index 09fece2..3f6d4e0 100644
--- a/code/compiler/12/ast.cpp
+++ b/code/compiler/12/ast.cpp
@@ -331,6 +331,70 @@ void ast_let::compile(const env_ptr& env, std::vector<instruction_ptr>& into) co
     into.push_back(instruction_ptr(new instruction_slide(translated_definitions.size())));
 }
 
+void ast_lambda::print(int indent, std::ostream&  to) const {
+    print_indent(indent, to);
+    to << "LAMBDA";
+    for(auto& param : params) {
+        to << " " << param;
+    }
+    to << std::endl;
+    body->print(indent+1, to);
+}
+
+void ast_lambda::find_free(std::set<std::string>& into) {
+    body->find_free(free_variables);
+    for(auto& param : params) {
+        free_variables.erase(param);
+    }
+    into.insert(free_variables.begin(), free_variables.end());
+}
+
+type_ptr ast_lambda::typecheck(type_mgr& mgr, type_env_ptr& env) {
+    this->env = env;
+    var_env = type_scope(env);
+    type_ptr 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();
+        var_env->bind(*it, param_type);
+        full_type = type_ptr(new type_arr(std::move(param_type), full_type));
+    }
+
+    mgr.unify(return_type, body->typecheck(mgr, var_env));
+    return full_type;
+}
+
+void ast_lambda::translate(global_scope& scope) {
+    std::vector<std::string> function_params;
+    for(auto& free_variable : free_variables) {
+        if(env->is_global(free_variable)) continue;
+        function_params.push_back(free_variable);
+    }
+    size_t captured_count = function_params.size();
+    function_params.insert(function_params.end(), params.begin(), params.end());
+
+    auto& new_function = scope.add_function("lambda", std::move(function_params), std::move(body));
+    type_env_ptr mangled_env = type_scope(env);
+    mangled_env->bind("lambda", type_scheme_ptr(nullptr), visibility::global);
+    mangled_env->set_mangled_name("lambda", new_function.name);
+    ast_ptr new_application = ast_ptr(new ast_lid("lambda"));
+    new_application->env = mangled_env;
+
+    for(auto& param : new_function.params) {
+        if(!(captured_count--)) break;
+        ast_ptr new_arg = ast_ptr(new ast_lid(param));
+        new_arg->env = env;
+        new_application = ast_ptr(new ast_app(std::move(new_application), std::move(new_arg)));
+        new_application->env = env;
+    }
+    translated = std::move(new_application);
+}
+
+void ast_lambda::compile(const env_ptr& env, std::vector<instruction_ptr>& into) const {
+    translated->compile(env, into);
+}
+
 void pattern_var::print(std::ostream& to) const {
     to << var;
 }
diff --git a/code/compiler/12/ast.hpp b/code/compiler/12/ast.hpp
index 29de43e..1e2f8b5 100644
--- a/code/compiler/12/ast.hpp
+++ b/code/compiler/12/ast.hpp
@@ -146,6 +146,25 @@ struct ast_let : public ast {
     void compile(const env_ptr& env, std::vector<instruction_ptr>& into) const;
 };
 
+struct ast_lambda : public ast {
+    std::vector<std::string> params;
+    ast_ptr body;
+
+    type_env_ptr var_env;
+
+    std::set<std::string> free_variables;
+    ast_ptr translated;
+
+    ast_lambda(std::vector<std::string> ps, ast_ptr b)
+        : params(std::move(ps)), body(std::move(b)) {}
+
+    void print(int indent, std::ostream& to) const;
+    void find_free(std::set<std::string>& into);
+    type_ptr typecheck(type_mgr& mgr, type_env_ptr& env);
+    void translate(global_scope& scope);
+    void compile(const env_ptr& env, std::vector<instruction_ptr>& into) const;
+};
+
 struct pattern_var : public pattern {
     std::string var;
 
diff --git a/code/compiler/12/parser.y b/code/compiler/12/parser.y
index deb0d39..2dc1744 100644
--- a/code/compiler/12/parser.y
+++ b/code/compiler/12/parser.y
@@ -13,6 +13,7 @@ extern yy::parser::symbol_type yylex();
 
 %}
 
+%token BACKSLASH
 %token PLUS
 %token TIMES
 %token MINUS
@@ -44,7 +45,7 @@ extern yy::parser::symbol_type yylex();
 %type <std::vector<parsed_type_ptr>> typeList
 %type <definition_group> definitions
 %type <parsed_type_ptr> type nonArrowType typeListElement
-%type <ast_ptr> aAdd aMul case let app appBase
+%type <ast_ptr> aAdd aMul case let lambda app appBase
 %type <definition_data_ptr> data 
 %type <definition_defn_ptr> defn
 %type <branch_ptr> branch
@@ -100,6 +101,7 @@ appBase
     | OPAREN aAdd CPAREN { $$ = std::move($2); }
     | case { $$ = std::move($1); }
     | let { $$ = std::move($1); }
+    | lambda { $$ = std::move($1); }
     ;
 
 let
@@ -107,6 +109,11 @@ let
         { $$ = ast_ptr(new ast_let(std::move($3), std::move($7))); }
     ;
 
+lambda
+    : BACKSLASH lowercaseParams ARROW OCURLY aAdd CCURLY
+        { $$ = ast_ptr(new ast_lambda(std::move($2), std::move($5))); }
+    ;
+
 case
     : CASE aAdd OF OCURLY branches CCURLY 
         { $$ = ast_ptr(new ast_case(std::move($2), std::move($5))); }
diff --git a/code/compiler/12/scanner.l b/code/compiler/12/scanner.l
index c417de1..7b61504 100644
--- a/code/compiler/12/scanner.l
+++ b/code/compiler/12/scanner.l
@@ -13,6 +13,7 @@
 %%
 
 [ \n]+ {}
+\\ { return yy::parser::make_BACKSLASH(); }
 \+ { return yy::parser::make_PLUS(); }
 \* { return yy::parser::make_TIMES(); }
 - { return yy::parser::make_MINUS(); }