ADD: if-then-else statement.

doc/grammar.bnf

@@ -6,10 +6,14 @@ INSTR ::= EXPR
 | VARDECL
 | CONSTDECL
 | ASSIGN
+| IF
 
 VARDECL ::= let_mut ident assign EXPR
 CONSTDECL ::= let ident assign EXPR
 ASSIGN ::= ident assign EXPR
+IF ::= if EXPR THEN (else (IF | ELSE))?
+THEN ::= INSTR*
+ELSE ::= INSTR*
 
 EXPR ::= IMP
 

lib/Compiler.cpp

@@ -25,6 +25,51 @@ namespace roza
   {
     switch (root->type())
       {
+
+      case NODE_IF: {
+        m_sym.enter_scope();
+
+        std::vector<size_t> to_end;
+
+        std::function<void(std::shared_ptr<Node>)>
+          f = [&](std::shared_ptr<Node> n){
+            auto cond = n->child(0);
+            auto then = n->child(1);
+
+            compile_node(cond, prog);
+            size_t cond_addr = prog->size();
+            prog->push_instr(OP_BRF, 0);
+
+            compile_node(then, prog);
+
+            to_end.push_back(prog->size());
+            prog->push_instr(OP_BR, 0);
+
+            prog->set_param(cond_addr, prog->size());
+
+            if (n->size() > 2)
+              {
+                auto next = n->child(2);
+                compile_node(next, prog);
+              }
+          };
+
+        f(root);
+
+        for (auto addr: to_end)
+          {
+            prog->set_param(addr, prog->size());
+          }
+
+        m_sym.leave_scope();
+
+      } break;
+
+      case NODE_ELSE:
+      case NODE_THEN: {
+        compile_children(root, prog);
+      } break;
+
       case NODE_ASSERT: {
         compile_children(root, prog);
         prog->push_instr(OP_ASSERT);

lib/Lexer.cpp

@@ -8,6 +8,7 @@ namespace roza
     , m_loc { loc }
   {
     std::vector<std::tuple<std::string, NodeType, bool>> texts = {
+      {";", NODE_EOI, false},
       {"==", NODE_EQ, false},
       {"!=", NODE_NE, false},
       {"<=", NODE_LE, false},
@@ -27,6 +28,9 @@ namespace roza
     };
 
     std::vector<std::tuple<std::string, NodeType, bool>> keywords = {
+      {"if", NODE_IF, false},
+      {"else", NODE_ELSE, false},
+      {"end", NODE_END, false},
       {"let!", NODE_LET_MUT, false},
       {"let", NODE_LET, false},
       {"true", NODE_BOOL, true},

lib/Node.hpp

@@ -13,7 +13,8 @@
     G(NODE_EQ), G(NODE_NE), G(NODE_LT), G(NODE_LE), G(NODE_GT),         \
     G(NODE_GE), G(NODE_ASSERT), G(NODE_ASSERT_STATIC_FAIL),             \
     G(NODE_IDENT), G(NODE_ASSIGN), G(NODE_LET), G(NODE_LET_MUT),        \
-    G(NODE_VARDECL), G(NODE_CONSTDECL)
+    G(NODE_VARDECL), G(NODE_CONSTDECL), G(NODE_IF), G(NODE_ELSE),       \
+    G(NODE_THEN), G(NODE_END)
 
 namespace roza
 {

lib/Parser.cpp

@@ -159,6 +159,12 @@ namespace roza
         ensure(NODE_EOI);
         return root;
       }
+    else if (type_is(NODE_IF))
+      {
+        auto root = parse_if();
+        consume_all(NODE_EOI);
+        return root;
+      }
     else
       {
         auto root = parse_expr();
@@ -213,6 +219,55 @@ namespace roza
     return root;
   }
 
+  std::shared_ptr<Node> Parser::parse_if()
+  {
+    auto root = consume(NODE_IF);
+    root->add_child(parse_expr());
+    root->add_child(parse_then());
+
+    if (type_is(NODE_ELSE)
+        && type_is(NODE_IF, 1))
+      {
+        consume(NODE_ELSE);
+        root->add_child(parse_if());
+        return root;
+      }
+
+    if (type_is(NODE_ELSE))
+      {
+        root->add_child(parse_else());
+      }
+
+    consume(NODE_END);
+
+    return root;
+  }
+
+  std::shared_ptr<Node> Parser::parse_then()
+  {
+    auto root = std::make_shared<Node>(NODE_THEN, "", node()->loc());
+
+    while (!type_is(NODE_ELSE)
+           && !type_is(NODE_END))
+      {
+        root->add_child(parse_instr());
+      }
+
+    return root;
+  }
+
+  std::shared_ptr<Node> Parser::parse_else()
+  {
+    auto root = consume(NODE_ELSE);
+
+    while (!type_is(NODE_END))
+      {
+        root->add_child(parse_instr());
+      }
+
+    return root;
+  }
+
   std::shared_ptr<Node> Parser::parse_expr()
   {
     return parse_imp();

lib/Parser.hpp

@@ -36,6 +36,9 @@ namespace roza
     std::shared_ptr<Node> parse_vardecl();
     std::shared_ptr<Node> parse_constdecl();
     std::shared_ptr<Node> parse_assign();
+    std::shared_ptr<Node> parse_if();
+    std::shared_ptr<Node> parse_then();
+    std::shared_ptr<Node> parse_else();
 
     std::shared_ptr<Node> parse_expr();
     std::shared_ptr<Node> parse_imp();

lib/Program.cpp

@@ -45,6 +45,12 @@ namespace roza
     return index < m_values.size();
   }
 
+  void Program::set_param(size_t index, param_t param)
+  {
+    assert(index < m_instrs.size());
+    m_instrs[index].param = param;
+  }
+
   std::string Program::string() const
   {
     std::stringstream ss;

lib/Program.hpp

@@ -30,6 +30,8 @@ namespace roza
     std::shared_ptr<Value> value(size_t index) const;
     bool has_value(size_t index) const;
 
+    void set_param(size_t index, param_t param);
+
     std::string string() const;
 
   private:

lib/StaticPass.cpp

@@ -26,6 +26,20 @@ namespace roza
 
     switch (root->type())
       {
+      case NODE_IF: {
+        m_sym.enter_scope();
+        auto cond_type = resolver.find(root->child(0), m_sym);
+        check_types(root, std::make_shared<Type>(TY_BOOL), cond_type);
+        check_children(root);
+        m_sym.leave_scope();
+      } break;
+
+      case NODE_THEN:
+      case NODE_ELSE: {
+        check_children(root);
+      } break;
+
+
       case NODE_CONSTDECL: {
         check(root->child(1));
         m_sym.declare(root->child(0)->repr(), root->child(1));

lib/SymTable.cpp

@@ -11,59 +11,130 @@ namespace roza
   /*explicit*/ SymTable::SymTable(SymTable const& sym_table)
   {
     m_scope = sym_table.m_scope;
-
-    for (auto const& entry: sym_table.m_entries)
-      {
-        m_entries[entry.first] = entry.second;
-      }
+    m_entries = sym_table.m_entries;
   }
 
   /*virtual*/ SymTable::~SymTable()
   {
   }
 
+  void SymTable::enter_scope()
+  {
+    m_scope++;
+  }
+
+  void SymTable::leave_scope()
+  {
+    auto iter = std::begin(m_entries);
+
+    while (iter != std::end(m_entries))
+      {
+        if (iter->scope >= m_scope)
+          {
+            iter = m_entries.erase(iter);
+          }
+        else
+          {
+            iter++;
+          }
+      }
+
+    m_scope--;
+  }
+
   int SymTable::declare(std::string const& name, std::shared_ptr<Node> node)
   {
-    assert(!exists(name));
+    assert(!exists_in_scope(name));
 
-    m_entries.insert({name, SymEntry {
+    m_entries.push_back(SymEntry {
+        name,
         SymTable::addr++,
         m_scope,
         node,
         false
-        }});
+      });
 
     return SymTable::addr - 1;
   }
 
   int SymTable::declare_mut(std::string const& name, std::shared_ptr<Node> node)
   {
-    assert(!exists(name));
+    int addr = declare(name, node);
+    m_entries.back().is_mut = true;
 
-    m_entries.insert({name, SymEntry {
-          SymTable::addr++,
-          m_scope,
-          node,
-          true
-        }});
-
-    return SymTable::addr - 1;
+    return addr;
   }
 
   SymEntry& SymTable::find(std::string const& name)
   {
     assert(exists(name));
-    return m_entries[name];
+
+    size_t idx = 0;
+    int scope = -1;
+
+    size_t i = 0;
+
+    for (auto const& entry: m_entries)
+      {
+        if (entry.name == name && entry.scope > scope)
+          {
+            idx = i;
+            scope = entry.scope;
+          }
+
+        i++;
+      }
+
+    assert(scope >= 0);
+
+    return m_entries[idx];
   }
 
   SymEntry const& SymTable::find(std::string const& name) const
   {
     assert(exists(name));
-    return m_entries.at(name);
+
+    size_t idx = 0;
+    int scope = -1;
+
+    size_t i = 0;
+
+    for (auto const& entry: m_entries)
+      {
+        if (entry.name == name && entry.scope > scope)
+          {
+            idx = i;
+            scope = entry.scope;
+          }
+
+        i++;
+      }
+
+    assert(scope >= 0);
+
+    return m_entries[idx];
   }
 
   bool SymTable::exists(std::string const& name) const
   {
-    return m_entries.find(name) != std::end(m_entries);
+    for (auto const& entry: m_entries)
+      {
+        if (entry.name == name) { return true; }
+      }
+
+    return false;
+  }
+
+  bool SymTable::exists_in_scope(std::string const& name) const
+  {
+    for (auto const& entry: m_entries)
+      {
+        if (entry.name == name && entry.scope >= m_scope)
+          {
+            return true;
+          }
+      }
+
+    return false;
   }
 }

lib/SymTable.hpp

@@ -7,6 +7,7 @@
 namespace roza
 {
   struct SymEntry {
+    std::string name;
     int addr;
     int scope;
     std::shared_ptr<Node> node;
@@ -21,6 +22,9 @@ namespace roza
 
     virtual ~SymTable();
 
+    void enter_scope();
+    void leave_scope();
+
     int declare(std::string const& name, std::shared_ptr<Node> node);
     int declare_mut(std::string const& name, std::shared_ptr<Node> node);
 
@@ -28,10 +32,11 @@ namespace roza
     SymEntry const& find(std::string const& name) const;
 
     bool exists(std::string const& name) const;
+    bool exists_in_scope(std::string const& name) const;
 
   private:
     static int addr;
-    std::unordered_map<std::string, SymEntry> m_entries;
+    std::vector<SymEntry> m_entries;
     int m_scope = 0;
   };
 }

lib/VM.cpp

@@ -19,6 +19,24 @@ namespace roza
       {
         switch (program->opcode(m_pc))
           {
+
+          case OP_BRF: {
+            auto value = program->value(pop());
+
+            if (!value->as_bool())
+              {
+                m_pc = *program->param(m_pc);
+              }
+            else
+              {
+                m_pc++;
+              }
+          } break;
+
+          case OP_BR: {
+            m_pc = *program->param(m_pc);
+          } break;
+
           case OP_LOAD_GLOBAL: {
             int addr = *program->param(m_pc);
             auto value = m_globals[addr];

lib/commons.hpp

@@ -1,6 +1,7 @@
 #ifndef roza_COMMONS_HPP
 #define roza_COMMONS_HPP
 
+#include <algorithm>
 #include <iostream>
 #include <vector>
 #include <memory>

lib/opcodes.hpp

@@ -9,7 +9,7 @@
     G(OP_IADD), G(OP_ISUB), G(OP_IMUL), G(OP_IDIV), G(OP_IMOD), G(OP_IPOW), \
     G(OP_MOD), G(OP_IUADD), G(OP_IUSUB), G(OP_AND), G(OP_OR), G(OP_NOT), \
     G(OP_IMP), G(OP_EQ), G(OP_ILT), G(OP_IGT), G(OP_ASSERT), G(OP_STORE_GLOBAL), \
-    G(OP_LOAD_GLOBAL)
+    G(OP_LOAD_GLOBAL), G(OP_BRF), G(OP_BR)
 
 namespace roza
 {

roza_tests/test_if.roza

@@ -0,0 +1,92 @@
+let! a = 0
+
+if true
+   a = 7
+end
+
+assert 7 == a
+
+if false
+   a = 9
+end
+
+assert 7 == a
+
+if true
+   a = 0
+else
+   a = 1
+end
+
+assert 0 == a
+
+if false
+   a = 0
+else
+   a = 1
+end
+
+assert 1 == a
+
+if true
+   a = 1
+else if true
+   a = 2
+else if true
+  a = 3
+else
+  a = 4
+end
+
+assert 1 == a
+
+if false
+   a = 1
+else if true
+   a = 2
+else if true
+  a = 3
+else
+  a = 4
+end
+
+assert 2 == a
+
+if false
+   a = 1
+else if false
+   a = 2
+else if true
+   a = 3
+else
+   a = 4
+end
+
+assert 3 == a
+
+if false
+   a = 1
+else if false
+   a = 2
+else if false
+  a = 3
+else
+  a = 4
+end
+
+assert 4 == a
+
+let! b = 54
+let! c = 33
+
+if true
+  let! b = 18
+  c = 7
+  assert 18 == b
+end
+
+assert 54 == b
+assert 7 == c
+
+
+assert_static_fail if 4 0; end

tests/Lexer.cpp

@@ -103,3 +103,12 @@ TEST_CASE_METHOD(LexerTest, "Lexer_declarations")
   REQUIRE("ASSIGN" == get_str(3));
   REQUIRE("" == get_str(4));
 }
+
+TEST_CASE_METHOD(LexerTest, "Lexer_if")
+{
+  m_lexer.scan(" if else end ");
+  REQUIRE("IF" == get_str(0));
+  REQUIRE("ELSE" == get_str(1));
+  REQUIRE("END" == get_str(2));
+  REQUIRE("" == get_str(3));
+}

tests/Parser.cpp

@@ -122,3 +122,18 @@ TEST_CASE_METHOD(ParserTest, "Parser_vardecl")
   test_node("PROG(CONSTDECL(IDENT[_coucou],MUL(INT[6],INT[7])))",
             "let _coucou = 6 * 7");
 }
+
+TEST_CASE_METHOD(ParserTest, "Parser_if")
+{
+  test_node("PROG(IF(BOOL[true],THEN(ASSIGN(IDENT[x],INT[4]))))",
+            "if true x = 4; end");
+
+  test_node("PROG(IF(BOOL[true],THEN(INT[1]),ELSE(INT[4])))",
+            "if true 1; else 4; end");
+
+  test_node("PROG(IF(BOOL[true],THEN(INT[0]),"
+            "IF(BOOL[false],THEN(INT[1]),"
+            "IF(BOOL[true],THEN(INT[2]),"
+            "ELSE(INT[3])))))",
+            "if true 0; else if false 1; else if true 2; else 3; end");
+}