From 227a9b7a25373e5a56712369cefdc98c823ebdbe Mon Sep 17 00:00:00 2001
From: bog <bog@gozmail.net>
Date: Sun, 10 Sep 2023 09:59:51 +0200
Subject: [PATCH] ADD: function literal (no closure yet).

---
 doc/grammar.bnf    |  4 +++
 lib/Code.cpp       |  5 +++
 lib/Code.hpp       |  3 ++
 lib/Compiler.cpp   | 50 ++++++++++++++++++++--------
 lib/Compiler.hpp   |  7 ++--
 lib/Function.cpp   | 12 ++++++-
 lib/Function.hpp   |  6 ++++
 lib/Lexer.cpp      |  1 +
 lib/Node.hpp       |  7 +++-
 lib/Opcodes.hpp    |  1 +
 lib/Parser.cpp     | 44 +++++++++++++++++++++++++
 lib/Parser.hpp     |  3 ++
 lib/Program.cpp    |  1 +
 lib/StaticPass.cpp | 21 +++++++++++-
 lib/SymTable.cpp   | 21 ++++++++++--
 lib/SymTable.hpp   |  6 +++-
 lib/VM.cpp         | 82 +++++++++++++++++++++++++++++++++++++++-------
 lib/VM.hpp         |  5 +++
 src/main.cpp       |  4 +--
 tests/Lexer.cpp    |  8 +++++
 tests/Parser.cpp   | 17 ++++++++++
 21 files changed, 270 insertions(+), 38 deletions(-)

diff --git a/doc/grammar.bnf b/doc/grammar.bnf
index 050043d..f3a9f41 100644
--- a/doc/grammar.bnf
+++ b/doc/grammar.bnf
@@ -3,6 +3,10 @@ EXPR ::=
 LITERAL
 | FUNCALL
 | VARDECL
+| LAMBDA
+LAMBDA ::= opar rarrow opar PARAMS cpar BODY cpar
+PARAMS ::= ident*
+BODY ::= expr*
 VARDECL ::= opar decl ident EXPR cpar
 FUNCALL ::= opar ident EXPR* cpar
 LITERAL ::= int | ident
diff --git a/lib/Code.cpp b/lib/Code.cpp
index 125f13c..cc177cb 100644
--- a/lib/Code.cpp
+++ b/lib/Code.cpp
@@ -7,6 +7,11 @@ namespace jk
   {
   }
 
+  /*explicit*/ Code::Code(std::shared_ptr<Program> program)
+    : m_program { program }
+  {
+  }
+
   /*virtual*/ Code::~Code()
   {
   }
diff --git a/lib/Code.hpp b/lib/Code.hpp
index 654c79e..493ee5f 100644
--- a/lib/Code.hpp
+++ b/lib/Code.hpp
@@ -10,12 +10,15 @@ namespace jk
   {
   public:
     explicit Code(foreign_t foreign);
+    explicit Code(std::shared_ptr<Program> program);
     virtual ~Code();
 
     foreign_t foreign() const { return m_foreign; }
+    std::shared_ptr<Program> program() const { return m_program; }
 
   private:
     foreign_t m_foreign;
+    std::shared_ptr<Program> m_program;
   };
 }
 
diff --git a/lib/Compiler.cpp b/lib/Compiler.cpp
index 111d1e6..45f489c 100644
--- a/lib/Compiler.cpp
+++ b/lib/Compiler.cpp
@@ -4,10 +4,8 @@
 
 namespace jk
 {
-  /*explicit*/ Compiler::Compiler(std::shared_ptr<SymTable> sym,
-                                  Logger& logger)
-    : m_sym { sym }
-    , m_logger(logger)
+  /*explicit*/ Compiler::Compiler(Logger& logger)
+    : m_logger(logger)
   {
   }
 
@@ -16,21 +14,23 @@ namespace jk
   }
 
   void Compiler::compile(std::shared_ptr<Node> node,
-                         std::shared_ptr<Program> program)
+                         std::shared_ptr<Program> program,
+                         std::shared_ptr<SymTable> sym)
   {
     switch (node->type())
       {
-      case NODE_PROG: {
+      case NODE_PROG:
+      case NODE_BODY: {
         for (size_t i=0; i<node->size(); i++)
           {
-            compile(node->child(i).lock(), program);
+            compile(node->child(i).lock(), program, sym);
           }
       } break;
 
       case NODE_FUNCALL: {
         for (size_t i=0; i<node->size(); i++)
           {
-            compile(node->child(i).lock(), program);
+            compile(node->child(i).lock(), program, sym);
           }
 
         program->push_instr(OPCODE_CALL, node->size() - 1);
@@ -38,26 +38,50 @@ namespace jk
 
       case NODE_VARDECL: {
         std::string ident = node->child(0).lock()->repr();
-        auto entry = m_sym->find(ident);
+        auto entry = sym->find(ident);
         assert(entry);
 
-        compile(node->child(1).lock(), program);
+        compile(node->child(1).lock(), program, sym);
         program->push_instr(OPCODE_STORE, entry->addr);
       } break;
 
+      case NODE_LAMBDA: {
+        auto params = node->child(0).lock();
+        auto body = node->child(1).lock();
+        auto prog = std::make_shared<Program>();
+        auto fun_sym = std::make_shared<SymTable>(m_logger, sym);
+
+        for (size_t i=0; i<params->size(); i++)
+          {
+            std::string param = params->child(i).lock()->repr();
+            fun_sym->declare(param,
+                         std::make_shared<Type>(TYPE_NIL),
+                         node->loc());
+          }
+
+        compile(body, prog, fun_sym);
+        prog->push_instr(OPCODE_RET);
+
+        auto code = std::make_shared<Code>(prog);
+        size_t addr = program->push_constant(Value::make_code(code));
+        program->push_instr(OPCODE_PUSH_CONST, addr);
+        program->push_instr(OPCODE_MK_FUNCTION);
+        //program->push_instr(OpcodeType opcode)
+      } break;
+
       case NODE_IDENT: {
         std::string ident = node->repr();
-        auto sym = m_sym->find(ident);
+        auto mysym = sym->find(ident);
         assert(sym);
 
         OpcodeType op_load = OPCODE_LOAD;
 
-        if (sym->is_global)
+        if (mysym->is_global)
           {
             op_load = OPCODE_LOAD_GLOBAL;
           }
 
-        program->push_instr(op_load, sym->addr);
+        program->push_instr(op_load, mysym->addr);
 
       } break;
 
diff --git a/lib/Compiler.hpp b/lib/Compiler.hpp
index cbeec58..6a6a898 100644
--- a/lib/Compiler.hpp
+++ b/lib/Compiler.hpp
@@ -15,15 +15,14 @@ namespace jk
   class Compiler
   {
   public:
-    explicit Compiler(std::shared_ptr<SymTable> sym,
-                      Logger& logger);
+    explicit Compiler(Logger& logger);
     virtual ~Compiler();
 
     void compile(std::shared_ptr<Node> node,
-                 std::shared_ptr<Program> program);
+                 std::shared_ptr<Program> program,
+                 std::shared_ptr<SymTable> sym);
 
   private:
-    std::shared_ptr<SymTable> m_sym;
     Logger& m_logger;
   };
 }
diff --git a/lib/Function.cpp b/lib/Function.cpp
index ae6a9f8..0289535 100644
--- a/lib/Function.cpp
+++ b/lib/Function.cpp
@@ -8,12 +8,22 @@ namespace jk
   {
   }
 
+  /*explicit*/ Function::Function(std::shared_ptr<Program> program)
+    : m_program { program }
+  {
+  }
+
   /*virtual*/ Function::~Function()
   {
   }
 
   value_t Function::call(std::vector<value_t> const& args)
   {
-    return m_foreign(args);
+    if (m_foreign)
+      {
+        return m_foreign(args);
+      }
+
+    return Value::make_nil();
   }
 }
diff --git a/lib/Function.hpp b/lib/Function.hpp
index 4fda67f..d5c943e 100644
--- a/lib/Function.hpp
+++ b/lib/Function.hpp
@@ -2,6 +2,7 @@
 #define jk_FUNCTION_HPP
 
 #include "commons.hpp"
+#include "Program.hpp"
 
 namespace jk
 {
@@ -14,12 +15,17 @@ namespace jk
   {
   public:
     explicit Function(foreign_t foreign);
+    explicit Function(std::shared_ptr<Program> program);
+
     virtual ~Function();
 
+    std::shared_ptr<Program> program() const { return m_program; }
+
     value_t call(std::vector<value_t> const& args);
 
   private:
     foreign_t m_foreign;
+    std::shared_ptr<Program> m_program;
   };
 }
 
diff --git a/lib/Lexer.cpp b/lib/Lexer.cpp
index a65b352..4c06dfd 100644
--- a/lib/Lexer.cpp
+++ b/lib/Lexer.cpp
@@ -7,6 +7,7 @@ namespace jk
     , m_loc { loc }
   {
     std::vector<std::tuple<NodeType, std::string, bool>> texts = {
+      {NODE_RARROW, "->", false},
       {NODE_DECL, "$", false},
       {NODE_OPAR, "(", false},
       {NODE_CPAR, ")", false}
diff --git a/lib/Node.hpp b/lib/Node.hpp
index 5363772..73908f5 100644
--- a/lib/Node.hpp
+++ b/lib/Node.hpp
@@ -12,7 +12,12 @@
     G(NODE_IDENT),                              \
     G(NODE_DECL),                               \
     G(NODE_FUNCALL),                            \
-    G(NODE_VARDECL)
+    G(NODE_VARDECL),                            \
+    G(NODE_RARROW),                             \
+    G(NODE_LAMBDA),                             \
+    G(NODE_PARAMS),                             \
+    G(NODE_BODY),
+
 
 
 namespace jk
diff --git a/lib/Opcodes.hpp b/lib/Opcodes.hpp
index fb8d941..f23c1d9 100644
--- a/lib/Opcodes.hpp
+++ b/lib/Opcodes.hpp
@@ -9,6 +9,7 @@
     G(OPCODE_LOAD),                             \
     G(OPCODE_STORE),                            \
     G(OPCODE_LOAD_GLOBAL),                      \
+    G(OPCODE_RET),                              \
     G(OPCODE_MK_FUNCTION)
 
 namespace jk
diff --git a/lib/Parser.cpp b/lib/Parser.cpp
index 573b7f7..72b3116 100644
--- a/lib/Parser.cpp
+++ b/lib/Parser.cpp
@@ -111,6 +111,12 @@ namespace jk
         return parse_vardecl();
       }
 
+    if (type_is(NODE_OPAR)
+        && type_is(NODE_RARROW, 1))
+      {
+        return parse_lambda();
+      }
+
     return parse_literal();
   }
 
@@ -126,6 +132,44 @@ namespace jk
     return root;
   }
 
+  std::shared_ptr<Node> Parser::parse_lambda()
+  {
+    auto root = std::make_shared<Node>(NODE_LAMBDA, "", loc());
+    consume(NODE_OPAR);
+    consume(NODE_RARROW);
+    consume(NODE_OPAR);
+    root->add_child(parse_params());
+    consume(NODE_CPAR);
+    root->add_child(parse_body());
+    consume(NODE_CPAR);
+
+    return root;
+  }
+
+  std::shared_ptr<Node> Parser::parse_params()
+  {
+    auto root = std::make_shared<Node>(NODE_PARAMS, "", loc());
+
+    while (!type_is(NODE_CPAR))
+      {
+        root->add_child(consume(NODE_IDENT));
+      }
+
+    return root;
+  }
+
+  std::shared_ptr<Node> Parser::parse_body()
+  {
+    auto root = std::make_shared<Node>(NODE_BODY, "", loc());
+
+    while (!type_is(NODE_CPAR))
+      {
+        root->add_child(parse_expr());
+      }
+
+    return root;
+  }
+
   std::shared_ptr<Node> Parser::parse_funcall()
   {
     auto root = std::make_shared<Node>(NODE_FUNCALL, "", loc());
diff --git a/lib/Parser.hpp b/lib/Parser.hpp
index d96c09f..9830478 100644
--- a/lib/Parser.hpp
+++ b/lib/Parser.hpp
@@ -32,6 +32,9 @@ namespace jk
     std::shared_ptr<Node> parse_prog();
     std::shared_ptr<Node> parse_expr();
     std::shared_ptr<Node> parse_vardecl();
+    std::shared_ptr<Node> parse_lambda();
+    std::shared_ptr<Node> parse_params();
+    std::shared_ptr<Node> parse_body();
     std::shared_ptr<Node> parse_funcall();
     std::shared_ptr<Node> parse_literal();
   };
diff --git a/lib/Program.cpp b/lib/Program.cpp
index 46b8bf7..a514921 100644
--- a/lib/Program.cpp
+++ b/lib/Program.cpp
@@ -48,6 +48,7 @@ namespace jk
 
   size_t Program::push_constant(std::shared_ptr<Value> value)
   {
+    assert(value);
     m_constants.push_back(value);
     return m_constants.size() - 1;
   }
diff --git a/lib/StaticPass.cpp b/lib/StaticPass.cpp
index bbe99a5..3f97509 100644
--- a/lib/StaticPass.cpp
+++ b/lib/StaticPass.cpp
@@ -17,7 +17,8 @@ namespace jk
   {
     switch (node->type())
       {
-      case NODE_PROG: {
+      case NODE_PROG:
+      case NODE_BODY: {
         for (size_t i=0; i<node->size(); i++)
           {
             pass(node->child(i).lock());
@@ -25,6 +26,24 @@ namespace jk
           }
       } break;
 
+      case NODE_LAMBDA: {
+        auto params = node->child(0).lock();
+        auto body = node->child(1).lock();
+
+        for (size_t i=0; i<params->size(); i++)
+          {
+            auto param = params->child(i).lock();
+            std::string ident = params->child(i).lock()->repr();
+            m_sym->declare(ident,
+                           std::make_shared<Type>(TYPE_NIL),
+                           param->loc());
+          }
+
+        pass(body);
+
+        push(std::make_shared<Type>(TYPE_FUNCTION));
+      } break;
+
       case NODE_INT: {
         push(std::make_shared<Type>(TYPE_INT));
       } break;
diff --git a/lib/SymTable.cpp b/lib/SymTable.cpp
index 70603a1..4bc3d51 100644
--- a/lib/SymTable.cpp
+++ b/lib/SymTable.cpp
@@ -2,8 +2,10 @@
 
 namespace jk
 {
-  /*explicit*/ SymTable::SymTable(Logger& logger)
+  /*explicit*/ SymTable::SymTable(Logger& logger,
+                                  std::shared_ptr<SymTable> parent)
     : m_logger { logger }
+    , m_parent { parent }
   {
   }
 
@@ -16,7 +18,7 @@ namespace jk
                     std::shared_ptr<Type> type,
                     Loc const& loc)
   {
-    if (find(name))
+    if (find_local(name))
       {
         m_logger.log<symbolic_error>(LOG_ERROR,
                                      loc,
@@ -49,7 +51,7 @@ namespace jk
     return addr;
   }
 
-  std::optional<Sym> SymTable::find(std::string const& name) const
+  std::optional<Sym> SymTable::find_local(std::string const& name) const
   {
     for (auto const& sym: m_syms)
       {
@@ -61,4 +63,17 @@ namespace jk
 
     return std::nullopt;
   }
+
+  std::optional<Sym> SymTable::find(std::string const& name) const
+  {
+    auto entry = find_local(name);
+    if (entry) { return entry; }
+
+    if (m_parent)
+      {
+        return m_parent->find(name);
+      }
+
+    return std::nullopt;
+  }
 }
diff --git a/lib/SymTable.hpp b/lib/SymTable.hpp
index 0696ca4..f7b1e05 100644
--- a/lib/SymTable.hpp
+++ b/lib/SymTable.hpp
@@ -20,7 +20,9 @@ namespace jk
   class SymTable
   {
   public:
-    explicit SymTable(Logger& logger);
+    explicit SymTable(Logger& logger,
+                      std::shared_ptr<SymTable> parent=nullptr);
+
     virtual ~SymTable();
 
     size_t declare(std::string const& name,
@@ -32,9 +34,11 @@ namespace jk
                           Loc const& loc);
 
     std::optional<Sym> find(std::string const& name) const;
+    std::optional<Sym> find_local(std::string const& name) const;
 
   private:
     Logger& m_logger;
+    std::shared_ptr<SymTable> m_parent;
     std::vector<Sym> m_syms;
     size_t m_addr = 0;
   };
diff --git a/lib/VM.cpp b/lib/VM.cpp
index d426f69..8a1b404 100644
--- a/lib/VM.cpp
+++ b/lib/VM.cpp
@@ -18,7 +18,11 @@ namespace jk
     Frame frame;
     frame.program = program;
     m_frames.push_back(frame);
+    execute();
+  }
 
+  void VM::execute()
+  {
     while (m_pc < m_frames.back().program->size())
       {
         Instr instr = m_frames.back().program->get(m_pc);
@@ -26,17 +30,28 @@ namespace jk
         switch (instr.opcode)
           {
           case OPCODE_MK_FUNCTION: {
-            auto code = program->constant(pop());
+            auto code = program()->constant(pop());
 
-            auto function = std::make_shared<Function>
-              (code->as_code()->foreign());
+            auto prog = code->as_code()->program();
+
+            std::shared_ptr<Function> function;
+
+            if (prog)
+              {
+                function = std::make_shared<Function>(prog);
+              }
+            else
+              {
+                 function = std::make_shared<Function>
+                  (code->as_code()->foreign());
+              }
 
             auto value = Value::make_function(function);
 
             size_t addr = push_heap(value);
             auto ref = Value::make_ref(addr);
 
-            push(program->push_constant(ref));
+            push(program()->push_constant(ref));
 
             m_pc++;
 
@@ -49,7 +64,7 @@ namespace jk
 
           case OPCODE_LOAD: {
             auto value = m_frames.back().locals[*instr.param];
-            push(program->push_constant(value));
+            push(program()->push_constant(value));
             m_pc++;
           } break;
 
@@ -57,35 +72,73 @@ namespace jk
             auto idx = pop();
 
             m_frames.back().locals[*instr.param] =
-              program->constant(idx);
+              program()->constant(idx);
 
             m_pc++;
           } break;
 
           case OPCODE_LOAD_GLOBAL: {
             auto value = m_globals[*instr.param];
-            push(program->push_constant(value));
+            push(program()->push_constant(value));
             m_pc++;
           } break;
 
+          case OPCODE_RET: {
+            size_t pc = m_frames.back().ret_addr;
+            size_t stack_sz = m_frames.back().stack_sz;
+            auto prog = m_frames.back().program;
+
+            param_t ret = pop();
+            auto ret_val = prog->constant(ret);
+            assert(ret_val);
+
+            while (m_stack.size() > stack_sz)
+              {
+                pop();
+              }
+
+            m_frames.pop_back();
+
+            push(program()->push_constant(ret_val));
+
+            m_pc = pc + 1;
+          } break;
+
           case OPCODE_CALL: {
             std::vector<std::shared_ptr<Value>> args;
 
             for (size_t i=0; i<*instr.param; i++)
               {
-                args.insert(std::begin(args), program->constant(pop()));
+                args.insert(std::begin(args), program()->constant(pop()));
               }
 
-            auto ref_val = program->constant(pop());
+            auto ref_val = program()->constant(pop());
             auto ref = ref_val->as_ref();
             auto fun_val = heap(ref);
             auto fun = fun_val->as_function();
 
-            auto result = fun->call(args);
+            if (auto prog = fun->program();
+                prog)
+              {
+                Frame frame;
+                frame.program = prog;
+                frame.ret_addr = m_pc;
+                frame.stack_sz = m_stack.size();
+                m_pc = 0;
 
-            push(program->push_constant(result));
+                for (size_t i=0; i<args.size(); i++)
+                  {
+                    frame.locals[i] = args[i];
+                  }
 
-            m_pc++;
+                m_frames.push_back(frame);
+              }
+            else
+              {
+                auto result = fun->call(args);
+                push(program()->push_constant(result));
+                m_pc++;
+              }
           } break;
 
           default:
@@ -137,4 +190,9 @@ namespace jk
     m_stack.pop_back();
     return param;
   }
+
+  std::shared_ptr<Program> VM::program() const
+  {
+    return m_frames.back().program;
+  }
 }
diff --git a/lib/VM.hpp b/lib/VM.hpp
index 90a6bdd..b0e2e0f 100644
--- a/lib/VM.hpp
+++ b/lib/VM.hpp
@@ -9,6 +9,8 @@ namespace jk
   struct Frame {
     std::shared_ptr<Program> program;
     std::unordered_map<int, std::shared_ptr<Value>> locals;
+    size_t ret_addr;
+    size_t stack_sz;
   };
 
   class VM
@@ -18,6 +20,7 @@ namespace jk
     virtual ~VM();
 
     void execute(std::shared_ptr<Program> program);
+    void execute();
 
     std::string string() const;
 
@@ -35,6 +38,8 @@ namespace jk
 
     void push(param_t param);
     param_t pop();
+
+    std::shared_ptr<Program> program() const;
   };
 }
 
diff --git a/src/main.cpp b/src/main.cpp
index a9894b9..f43093c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -84,7 +84,7 @@ int main(int argc, char** argv)
       auto sym = std::make_shared<jk::SymTable>(logger);
 
 
-      auto compiler = std::make_shared<jk::Compiler>(sym, logger);
+      auto compiler = std::make_shared<jk::Compiler>(logger);
       auto program = std::make_shared<jk::Program>();
       auto vm = std::make_shared<jk::VM>();
       auto loader = std::make_shared<jk::Loader>(vm, sym);
@@ -93,7 +93,7 @@ int main(int argc, char** argv)
       auto static_pass = std::make_shared<jk::StaticPass>(sym, logger);
       static_pass->pass(ast);
 
-      compiler->compile(ast, program);
+      compiler->compile(ast, program, sym);
 
       if (debug_mode)
         {
diff --git a/tests/Lexer.cpp b/tests/Lexer.cpp
index b7d71f3..098db6f 100644
--- a/tests/Lexer.cpp
+++ b/tests/Lexer.cpp
@@ -73,3 +73,11 @@ TEST_CASE_METHOD(LexerTest, "Lexer_vardecl")
   test_next(*lexer, "DECL");
   test_end(*lexer);
 }
+
+TEST_CASE_METHOD(LexerTest, "Lexer_lambda")
+{
+  auto lexer = jk::Factory(m_logger, "tests/lexer").make_lexer();
+  lexer->scan(" -> ");
+  test_next(*lexer, "RARROW");
+  test_end(*lexer);
+}
diff --git a/tests/Parser.cpp b/tests/Parser.cpp
index 4c18aab..2160df6 100644
--- a/tests/Parser.cpp
+++ b/tests/Parser.cpp
@@ -44,3 +44,20 @@ TEST_CASE_METHOD(ParserTest, "Parser_vardecl")
               "FUNCALL(IDENT[f],INT[3],INT[2])))",
               " ($ world (f 3 2)) ");
 }
+
+TEST_CASE_METHOD(ParserTest, "Parser_lambda")
+{
+  test_parser("PROG(LAMBDA(PARAMS("
+              "IDENT[x],IDENT[y]"
+              "),BODY("
+              "FUNCALL(IDENT[add],IDENT[y],IDENT[x])"
+              ")))",
+              " (-> (x y) (add y x)) ");
+
+    test_parser("PROG(LAMBDA(PARAMS("
+                "IDENT[x]"
+                "),BODY("
+                "IDENT[x]"
+                ")))",
+                " (-> (x) x)");
+}