parser

I was taking a look at the source code of a known php library, called Twig (it is a template engine, with its own syntax), an ... t things? Sorry if I'm confused on the question, but I think the community will help me with a good and enlightening answer.

Reading about regular expression I saw a recurring term, DOM parser, and my doubts arose: What is DOM Parser? How does it work? every language has?

How can I convert request responses in XML format to objects in Swift, just like ObjectMapper does with JSON to objects?

Problem: develop the myhtmlparser class as a subclass of HTMLParser which, when fed with an HTML file, shows the names of the ... t p end h2 start h2 end ... a start a end body end html end How to fix the code so as to achieve indentation on the output?

I am developing this little program that should receive an expression from the user and do the calculation. Ex: Enter an ... ion sent by the user. I was recommended to use something like eval, but I did not find anything equivalent in the C language.