Tweak operators

Add back unary `+` and `-` as prefix operators (with `!` these are the natural, and currently only, prefix operators) Add recognizing `*` or `&` as must-be-binary if followed by a literal (as when followed by `(` or an identifier)

Author: hsutter

source/cppfront.cpp

@@ -1830,10 +1830,14 @@ class cppfront
  auto suffix = std::string{};
  for (auto const& x : n.ops) {
  assert(x);
- assert(x->type() == lexeme::Not); // should be the only prefix operator
- printer.add_pad_in_this_line(-3);
- printer.print_cpp2("!(", n.position());
- suffix += ")";
+ if (x->type() == lexeme::Not) {
+ printer.print_cpp2("!(", n.position());
+ printer.add_pad_in_this_line(-3);
+ suffix += ")";
+ }
+ else {
+ printer.print_cpp2(*x, x->position());
+ }
  }
  assert(n.expr);
  emit(*n.expr);

source/lex.h

@@ -95,6 +95,18 @@ enum class lexeme : std::int8_t {
  Identifier
 };
 
+auto is_literal(lexeme l) {
+ switch (l) {
+ break;case lexeme::FloatLiteral: 
+ case lexeme::BinaryLiteral: 
+ case lexeme::DecimalLiteral: 
+ case lexeme::HexadecimalLiteral: 
+ case lexeme::StringLiteral: 
+ case lexeme::CharacterLiteral: return true;
+ break;default: return false;
+ }
+}
+
 // TODO: Remove the duplication above/below with a variadic macro,
 // but for now it's simpler just to write it out
 

source/parse.h

@@ -37,7 +37,14 @@ auto violates_lifetime_safety = false;
 //G
 auto is_prefix_operator(lexeme l) -> bool
 {
- return l == lexeme::Not;
+ switch (l) {
+ break;case lexeme::Not:
+ case lexeme::Minus:
+ case lexeme::Plus:
+ return true;
+ break;default:
+ return false;
+ }
 }
 
 
@@ -1389,9 +1396,10 @@ class parser
  curr().type() == lexeme::Dot
  )
  {
- // * & and ~ can't be a unary operator if followed by ( or identifier
- if ((curr().type() == lexeme::Multiply || curr().type() == lexeme::Ampersand || curr().type() == lexeme::Tilde) &&
- (peek(1)->type() == lexeme::LeftParen || peek(1)->type() == lexeme::Identifier))
+ // * and & can't be a unary operator if followed by a (, identifier, or literal
+ if ((curr().type() == lexeme::Multiply || curr().type() == lexeme::Ampersand) &&
+ peek(1) &&
+ (peek(1)->type() == lexeme::LeftParen || peek(1)->type() == lexeme::Identifier || is_literal(peek(1)->type())))
  {
  break;
  }