From 03cc9b58e229691b995ba54295abdc5d1e34b5bf Mon Sep 17 00:00:00 2001
From: bog <bog@gozmail.net>
Date: Sun, 10 Sep 2023 11:10:30 +0200
Subject: [PATCH] ADD: function declaration syntaxic sugar.

---
 doc/grammar.bnf  |  2 ++
 lib/Parser.cpp   | 32 ++++++++++++++++++++++++++++++++
 lib/Parser.hpp   |  1 +
 tests/Parser.cpp | 10 ++++++++++
 4 files changed, 45 insertions(+)

diff --git a/doc/grammar.bnf b/doc/grammar.bnf
index f3a9f41..41ec2cc 100644
--- a/doc/grammar.bnf
+++ b/doc/grammar.bnf
@@ -3,10 +3,12 @@ EXPR ::=
 LITERAL
 | FUNCALL
 | VARDECL
+| FUNDECL
 | LAMBDA
 LAMBDA ::= opar rarrow opar PARAMS cpar BODY cpar
 PARAMS ::= ident*
 BODY ::= expr*
 VARDECL ::= opar decl ident EXPR cpar
+FUNDECL ::= opar decl opar ident PARAMS cpar EXPR cpar
 FUNCALL ::= opar ident EXPR* cpar
 LITERAL ::= int | ident
diff --git a/lib/Parser.cpp b/lib/Parser.cpp
index 72b3116..c2662a0 100644
--- a/lib/Parser.cpp
+++ b/lib/Parser.cpp
@@ -99,6 +99,13 @@ namespace jk
 
   std::shared_ptr<Node> Parser::parse_expr()
   {
+    if (type_is(NODE_OPAR)
+        && type_is(NODE_DECL, 1)
+        && type_is(NODE_OPAR, 2))
+      {
+        return parse_fundecl();
+      }
+
     if (type_is(NODE_OPAR)
         && type_is(NODE_IDENT, 1))
       {
@@ -132,6 +139,31 @@ namespace jk
     return root;
   }
 
+  std::shared_ptr<Node> Parser::parse_fundecl()
+  {
+    consume(NODE_OPAR);
+    consume(NODE_DECL);
+
+    consume(NODE_OPAR);
+    auto ident = consume(NODE_IDENT);
+    auto params = parse_params();
+
+    consume(NODE_CPAR);
+
+    auto body = parse_body();
+    consume(NODE_CPAR);
+
+    auto vardecl = std::make_shared<Node>(NODE_VARDECL, "", ident->loc());
+    vardecl->add_child(ident);
+
+    auto lambda = std::make_shared<Node>(NODE_LAMBDA, "", ident->loc());
+    lambda->add_child(params);
+    lambda->add_child(body);
+    vardecl->add_child(lambda);
+
+    return vardecl;
+  }
+
   std::shared_ptr<Node> Parser::parse_lambda()
   {
     auto root = std::make_shared<Node>(NODE_LAMBDA, "", loc());
diff --git a/lib/Parser.hpp b/lib/Parser.hpp
index 9830478..e6282fb 100644
--- a/lib/Parser.hpp
+++ b/lib/Parser.hpp
@@ -32,6 +32,7 @@ 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_fundecl();
     std::shared_ptr<Node> parse_lambda();
     std::shared_ptr<Node> parse_params();
     std::shared_ptr<Node> parse_body();
diff --git a/tests/Parser.cpp b/tests/Parser.cpp
index 2160df6..451e179 100644
--- a/tests/Parser.cpp
+++ b/tests/Parser.cpp
@@ -61,3 +61,13 @@ TEST_CASE_METHOD(ParserTest, "Parser_lambda")
                 ")))",
                 " (-> (x) x)");
 }
+
+TEST_CASE_METHOD(ParserTest, "Parser_fundecl")
+{
+  test_parser("PROG(VARDECL(IDENT[f],LAMBDA("
+              "PARAMS(IDENT[x],IDENT[y]),BODY("
+              "FUNCALL(IDENT[add],IDENT[y],IDENT[x])"
+              ")"
+              ")))",
+              " ($ (f x y) (add y x)) ");
+}