1 files changed, 144 insertions, 0 deletions
diff --git a/tiger-compiler/src/desugar/desugar-visitor.cc b/tiger-compiler/src/desugar/desugar-visitor.cc
new file mode 100644
index 0000000..770cdf6
--- /dev/null
+++ b/tiger-compiler/src/desugar/desugar-visitor.cc
@@ -0,0 +1,144 @@
+/**
+ ** \file desugar/desugar-visitor.cc
+ ** \brief Implementation of desugar::DesugarVisitor.
+ */
+
+#include <ast/all.hh>
+#include <ast/libast.hh>
+#include <desugar/desugar-visitor.hh>
+#include <misc/algorithm.hh>
+#include <misc/symbol.hh>
+#include <parse/libparse.hh>
+#include <parse/tweast.hh>
+
+namespace desugar
+{
+  DesugarVisitor::DesugarVisitor(bool desugar_for_p, bool desugar_string_cmp_p)
+    : super_type()
+    , desugar_for_p_(desugar_for_p)
+    , desugar_string_cmp_p_(desugar_string_cmp_p)
+  {}
+
+  /*-----------------------------.
+  | Desugar string comparisons.  |
+  `-----------------------------*/
+  void DesugarVisitor::operator()(const ast::OpExp& e)
+  {
+    // FIXME DONE: Some code was deleted here.
+    // Check to see that all of the elements to operate on are strings
+    if (dynamic_cast<const type::String*>(e.left_get().type_get()) == nullptr
+        || dynamic_cast<const type::String*>(e.right_get().type_get()) == nullptr)
+      {
+        return super_type::operator()(e);
+      }
+
+    const auto left = recurse(e.left_get());
+    const auto right = recurse(e.right_get());
+
+    misc::variant<ast::Exp*, ast::ChunkList*> res;
+
+    switch (e.oper_get())
+    {
+    case ast::OpExp::Oper::eq:
+    {
+        res = parse::parse(parse::Tweast() << "streq(" << left << ", " << right << ") = 0");
+        break;
+    }
+    case ast::OpExp::Oper::ne:
+    {
+        res = parse::parse(parse::Tweast() << "streq(" << left << ", " << right << ") <> 0");
+        break;
+    }
+    case ast::OpExp::Oper::lt:
+    {
+        res = parse::parse(parse::Tweast() << "strcmp(" << left << ", " << right << ") = -1");
+        break;
+    }
+    case ast::OpExp::Oper::le:
+    {
+        res = parse::parse(parse::Tweast() << "strcmp(" << left << ", " << right << ") <= 0");
+        break;
+    }
+    case ast::OpExp::Oper::gt:
+    {
+        res = parse::parse(parse::Tweast() << "strcmp(" << left << ", " << right << ") = 1");
+        break;
+    }
+    case ast::OpExp::Oper::ge:
+    {
+        res = parse::parse(parse::Tweast() << "strcmp(" << left << ", " << right << ") >= 0");
+        break;
+    }
+    default:
+        break;
+    }
+
+    ast::Exp* final = std::get<ast::Exp*>(res);
+    result_ = final;
+  }
+
+  /*----------------------.
+  | Desugar `for' loops.  |
+  `----------------------*/
+
+  /*<<-
+    Desugar `for' loops as `while' loops:
+
+       for i := lo to hi do
+         body
+
+     is transformed as:
+
+       let
+         var _lo := lo
+         var _hi := hi
+         var i := _lo
+       in
+         if i <= _hi then
+           while 1 do
+             (
+               body;
+               if i = _hi then
+                 break;
+               i := i + 1
+             )
+       end
+
+     Notice that:
+
+     - a `_hi' variable is introduced so that `hi' is evaluated only
+       once;
+
+     - a `_lo' variable is introduced to prevent `i' from being in the
+       scope of `_hi';
+
+     - a first test is performed before entering the loop, so that the
+       loop condition becomes `i < _hi' (instead of `i <= _hi'); this
+       is done to prevent overflows on INT_MAX.
+       ->>*/
+
+  void DesugarVisitor::operator()(const ast::ForExp& e)
+  {
+    // FIXME DONE: Some code was deleted here.
+    auto var_init = recurse(e.vardec_get().init_get());
+    auto lim = recurse(e.hi_get());
+    auto body = recurse(e.body_get());
+    auto iterator = e.vardec_get().name_get();
+    auto res = parse::parse(parse::Tweast() << "let "
+                            "var _lo := " << var_init <<
+                            " var _hi := " << lim <<
+                            " var " << iterator << " := _lo "
+                            "in "
+                            "if " << iterator << " <= _hi then "
+                            "while 1 do "
+                            "( " << body << ";"
+                            "if " << iterator << " = _hi then "
+                            "break;"
+                             << iterator << " := " << iterator << " + 1 "
+                            ") "
+                            "end");
+    ast::Exp* final = std::get<ast::Exp*>(res);
+    result_ = final;
+  }
+
+} // namespace desugar