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/**
** \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
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