BARES is an acronym to Basic ARithmetic Expression Evaluator based on Stacks. He receives a set of expressions from a input file (one by line) and computes all of them, when the expression is valid, returns your result, otherwise returns the error who turned him into a invalid expression with the column where he is (if is applicable).
Is a valid expression when all your terms are short int numbers (between -32768 and 32767), binary operators, parenthesis and the unary minus. Which are described on the following table.
| Symbol | Operation | Precedence Index |
|---|---|---|
| - | Minus (Unary and Binary) | 2 (unary) or 5 (binary) |
| + | Addition | 5 |
| * | Multiplication | 4 |
| / | Division | 4 |
| % | Modulo (Remainder after division) | 4 |
| ^ | Exponentiation | 3 |
| () | Parentheses (Break of precedence) | 1 |
To generate the expression result, this program needs to tokenize all elements, generating a queue with your terms.
After that, this queue of terms (in infix notation) needs to be converted to postfix notation (Reverse Polish Notation - RPN) to eliminate all parentheses (to avoid ambiguity), turning into a computable expression.
With the queue of terms in a postfix notation, a stack is used to make all calculations in right order (pushing and popping elements).
C is the column where the error was found at first time
- Numeric constant out of range: column C
- Ill-formed expression or missing term detected: column C
- Invalid operand: column C
- Extraneous symbol: column C
- Mismatch ')': column C
- Lost operator: column C
- Missing closing ')' to match opening '(' at: column C
- Division by zero!
- Numeric overflow error!
To compile you just need to run the following commands:
make clean
makeThis version will generate a output file with only the error ID. If you wanna see the fully error message, you need to declare the SHOW_ERROR_MESSAGE flag as true. Like:
make clean
make SHOW_ERROR_MESSAGE=trueNow, to execute:
./bin/bares input_file [output_file]Where the input_file and output_file are a plain text file located on data folder.
The output_file is a optional parameter, so if wasn't specified, the program will print the output on terminal screen.
This program was fully developed by Elton de Souza Vieira
The source files of BARES project are available on GitHub.