private bool NextTypeRequiresConcat(RegExToken.TokenType type)
{
switch (type)
{
case RegExToken.TokenType.Accept:
case RegExToken.TokenType.OperatorOpenParanthesis:
return true;
}
return false;
}
private bool PreceedingTypeRequiresConcat(RegExToken.TokenType type)
{
switch (type)
{
case RegExToken.TokenType.OperatorMul:
case RegExToken.TokenType.OperatorQuestion:
case RegExToken.TokenType.OperatorPlus:
case RegExToken.TokenType.Accept:
case RegExToken.TokenType.OperatorCloseParanthesis:
case RegExToken.TokenType.NumberedRepeat:
return true;
}
return false;
}
private IEnumerable <RegExToken> TokensWithImplicitConcat()
{
RegExToken lastToken = null;
for (var token = lexer.NextToken(); token != null;)
{
// If the last token was accept and this new token is also accept we need to insert a concat operator
// between the two.
if (lastToken != null &&
PreceedingTypeRequiresConcat(lastToken.Type) &&
NextTypeRequiresConcat(token.Type))
{
yield return(new RegExToken {
Type = RegExToken.TokenType.OperatorConcat
});
}
yield return(token);
lastToken = token;
token = lexer.NextToken();
}
}
