arothuis / antlr4-calculator Goto Github PK

It might be interesting to support floating-point numbers, rather than only integers (1.23).
We could also allow _ as a separator for more legible numbers (i.e. 1_000_000).

This requires adding and changing token names for better disambiguation.

I tested your calculator with the inputs below:

Calculate: 1-2
-1.0
Calculate: 1-2*3
-5.0
Calculate: 1-2*3+4
-9.0

This is wrong, 1-2*3+4 = -1.0

Start program with 'nl.arothuis.antlr4calculator.ListenerMain' or 'nl.arothuis.antlr4calculator.ListenerMain'
Calculate: 4-2
4.0
Calculate: 4+-2
2.0

This may due to "-" is treated as number, but how to fix it?

Things that would benefit education:

• the parser package is perhaps a misnomer: it contains behaviors rather than merely parsing (evaluator or translator might be more accurate names)
• tokens are too specific (and needlessly abbreviated): we're naming our tokens by the actions they belong to (which is semantically too specific), rather than how they look (which is more on the level of tokenization/lexing): CARET, PLUS, MINUS, STAR, SLASH, LEFT_PARENTHESIS, RIGHT_PARENTHESIS
• remove typos from comments

Hi,

Sorry to interrupt. Could you help me how to build this project in Intellij IDEA locally?

import nl.arothuis.antlr4calculator.core.parser.CalculatorLexer;
import nl.arothuis.antlr4calculator.core.parser.CalculatorParser;

It suggests that these two classes cannot be imported.

Right now, the parser is quite tolerant -- a bit too tolerant, perhaps.

For educational purposes, it might be a better idea to explicitly fail on a parse error and give the user some feedback on what went wrong.