/**
* @return true if the token stream in its present state can convert
* the token stream to a case expression.
*
* @param parser -- Parser that is used to parse out whole elements.
* @param stream -- The token stream.
* @param elements -- The element output, first element is the condition, every
* other element should be case element containers, and the
* last element could be a default element.
* @return true if the stream of tokens can be accepted, false otherwise.
*/
bool Case_::CanAccept_( Parser const& parser
, TokenStream& stream
, std::vector<strine::Element>& elements
) const
{
bool can_accept = MatchToken_(stream, "(")
&& MatchToken_(stream, "case");
if (can_accept && stream.HasTokens())
{
Element current_element;
can_accept =parser.ParseAny(stream, current_element);
elements.push_back(current_element);
}
else
{
can_accept = false;
}
while(can_accept && stream.HasTokens())
{
stream.Push();
bool isEnd = MatchToken_(stream, ")");
if (isEnd)
{
stream.Consume();
break;
}
// Reset the stream, attempt to parse a list.
stream.Rollback();
// Right now I'm not sure what symbol to use for an "ANY"- needs to
// be something self-explanatory.
bool isAlmostEnd = MatchToken_(stream, "->");
if (isAlmostEnd)
{
stream.Consume();
assert(0);
break;
}
stream.Rollback();
// Typically we'll have a condition.
can_accept = (MatchToken_(stream, "["))
&& CanAcceptListRemainder_(parser, stream, elements);
}
return can_accept;
}
/**
* A convenience method used for parsing out tokens, this is kind of a repetitive
* task so it has been written once here.
*
* @param ts The token stream to draw from.
* @param token The token as string to match.
* @return true if the token was matched, false otherwise.
*/
bool Case_::MatchToken_( TokenStream& ts
, std::string const& token) const
{
bool success = ts.HasTokens();
if (success)
{
Element currentElement = ts.NextToken();
int const TYPE = currentElement.Type();
std::string const VALUE(currentElement.ToString());
success = (TYPE == Types::TOKEN && VALUE == token);
}
return success;
}
/**
* Parse the end of the token stream.
*
* @param stream -- Stream that has been prepped.
*/
bool Builtin_::ParseEnd_(TokenStream& stream) const
{
bool is_end = false;
if (stream.HasTokens())
{
stream.Push();
Element current_element = stream.NextToken();
is_end = (current_element.Type() == Types::TOKEN
&& current_element.ToString() == ")" );
stream.Rollback();
}
return is_end;
}
/**
* Parse out any element possible EXCEPT FOR TOKENS!
*
* @param in -- THe token stream to parse from.
* @param element -- The element to populate if possible.
*
* @return true if something was parsed, false otherwise.
*/
bool Parser::ParseAny( TokenStream& in, Element& element ) const
{
bool success = false;
if (in.HasTokens())
{
in.Push();
// First rule of thumb, if the first element in the stream is non-token then
// return that element since it should be the first.
strine::Element current = in.NextToken();
if ( current.Type() != Types::TOKEN )
{
element = current;
success = true;
}
else
{
in.Rollback();
strine::Element element_out;
// Go through all the parsables in the container, and try to parse them.
// If it can be parsed, then do it.
size_t const PARSABLES_SIZE = this->parsables.size();
for(size_t i=0; i<PARSABLES_SIZE; ++i)
{
std::shared_ptr<ParsableElement_> parsable = this->parsables[i];
success = parsable->Process( *this
, in
, element_out );
if (success)
{
element = element_out;
break;
}
}
}
}
return success;
}
/**
* @return true if the token stream in its present state can convert
* the token stream to a set expression.
*
* @param in -- The token stream.
* @return true if the stream of tokens can be accepted, false otherwise.
*/
bool Function_::CanAccept_( Parser const& parser
, TokenStream& stream
, std::vector<strine::Element>& elements) const
{
bool can_accept = false;
// (
if (stream.HasTokens())
{
Element current_element = stream.NextToken();
can_accept = (current_element.Type() == Types::TOKEN)
&& (current_element.ToString() == "(");
}
// function
if (can_accept && stream.HasTokens())
{
Element current_element = stream.NextToken();
can_accept = (current_element.Type() == Types::TOKEN)
&& (current_element.ToString() == "function");
}
// (
if (can_accept && stream.HasTokens())
{
Element current_element = stream.NextToken();
can_accept = (current_element.Type() == Types::TOKEN)
&& (current_element.ToString() == "(");
}
// args
while(can_accept && stream.HasTokens())
{
strine::Element current_element = stream.NextToken();
if (current_element.Type() == Types::TOKEN)
{
if (current_element.ToString() == ")")
{
break;
}
else
{
can_accept = false;
}
}
else if (current_element.Type() == Types::VARIABLE)
{
elements.push_back(current_element);
}
else
{
can_accept = false;
}
}
if (can_accept)
{
stream.Push();
strine::Element new_body;
can_accept = parser.ParseAny(stream, new_body);
if (can_accept && stream.HasTokens())
{
stream.Consume();
Element current_element = stream.NextToken();
can_accept = (current_element.Type() == Types::TOKEN)
&& (current_element.ToString() == ")");
elements.push_back(new_body);
}
else
{
stream.Rollback();
can_accept = false;
}
}
return can_accept;
}
/**
* One of the key methods inside of parser can take a general description
* of what should be on the token stream and attempts to figure it out.
*
* @param in -- The input token stream.
* @param rules -- The set of input rules we tokenize by.
* @param elements -- The set of elements.
*
* @return true if the set of rules can be parsed, false otherwise.
*/
bool Parser::CanParse( TokenStream& in
, std::vector<ParseRule> const& rules
, std::vector<Element>& elements) const
{
bool success = true;
elements.clear();
size_t rule_index = 0;
while(in.HasTokens() && rule_index < rules.size())
{
// Grab the current rule.
ParseRule const& rule = rules[rule_index];
// Check to see if the current rule states that we expect a token,
// if this is the case, then try to match the next element as a
// token.
if (rule.Type() == strine::Types::TOKEN)
{
strine::Element current_element = in.NextToken();
std::string const rule_token(rule.Token());
std::string const element_string(current_element.ToString());
success = (rule_token == element_string);
}
// If the rule states that the type should be ANY, try to parse
// out any element by using ParseAny.
else if (rule.Type() == ParseRule::ANY)
{
strine::Element current_element;
// Push a marker onto the token stream.
in.Push();
success = ParseAny( in, current_element );
if (success)
{
elements.push_back(current_element);
}
else
{
in.Rollback();
}
}
// If the rule.Type() hasn't been specified, then go ahead and try
// to match up the types.
else
{
strine::Element current_element = in.NextToken();
if (rule.Type() == current_element.Type())
{
success = true;
elements.push_back(current_element);
}
else
{
success = false;
}
}
if (false == success)
{
break;
}
rule_index += 1;
}
if (rule_index < rules.size())
{
success = false;
}
return success;
}
/**
* @return true if the token stream in its present state can convert
* the token stream to a builtin expression.
*
* @param in -- The token stream.
* @return true if the stream of tokens can be accepted, false otherwise.
*/
bool Builtin_::CanAccept_( Parser const& parser
, TokenStream& stream
, std::vector<Element>& elements) const
{
bool can_accept = false;
// (
if (stream.HasTokens())
{
Element current_element = stream.NextToken();
can_accept = (current_element.Type() == Types::TOKEN)
&& (current_element.ToString() == "(");
}
can_accept = can_accept && stream.HasTokens();
// builtin
if (can_accept)
{
Element current_element = stream.NextToken();
can_accept = (current_element.Type() == Types::TOKEN)
&& (current_element.ToString() == "builtin");
}
can_accept = can_accept && stream.HasTokens();
// Symbol
if (can_accept)
{
Element current_element = stream.NextToken();
can_accept = (current_element.Type() == Types::STRING);
elements.push_back(current_element);
}
can_accept = can_accept && stream.HasTokens();
//
if (can_accept)
{
if (ParseEnd_(stream))
{
stream.NextToken();
}
else
{
Element current_element;
stream.Push();
can_accept = parser.ParseAny( stream, current_element );
if (false == can_accept)
{
stream.Rollback();
}
else
{
elements.push_back(current_element);
stream.Consume();
}
can_accept = ParseEnd_(stream);
if (can_accept)
{
stream.NextToken();
}
}
}
return can_accept;
}