Parsing an arithmetic expression and building a tree from it in Java
- by ChocolateBear
Hi, I needed some help with creating custom trees given an arithmetic expression. Say, for example, you input this arithmetic expression:
(5+2)*7
The result tree should look like:
*
/ \
+ 7
/ \
5 2
I have some custom classes to represent the different types of nodes, i.e. PlusOp, LeafInt, etc. I don't need to evaluate the expression, just create the tree, so I can perform other functions on it later.
Additionally, the negative operator '-' can only have one child, and to represent '5-2', you must input it as 5 + (-2).
Some validation on the expression would be required to ensure each type of operator has the correct the no. of arguments/children, each opening bracket is accompanied by a closing bracket.
Also, I should probably mention my friend has already written code which converts the input string into a stack of tokens, if that's going to be helpful for this.
I'd appreciate any help at all. Thanks :)
(I read that you can write a grammar and use antlr/JavaCC, etc. to create the parse tree, but I'm not familiar with these tools or with writing grammars, so if that's your solution, I'd be grateful if you could provide some helpful tutorials/links for them.)
