A calculator program in Java that evaluates expressions in a very simple integer expression language. The program takes an input on the command line, computes the result, and prints it to the console. For example:
java -cp target/calculator_<version>.jar calculator.Main "let(a, 5, add(a, a))"
4
Note: the jar file is the result of building the project using maven.
Here are a few examples:
| Input | Output |
|---|---|
| add(1, 2) | 3 |
| add(1, mult(2, 3)) | 7 |
| mult(add(2, 2), div(9, 3)) | 12 |
| let(a, 5, add(a, a)) | 10 |
| let(a, 5, let(b, mult(a, 10), add(b, a))) | 55 |
| let(a, let(b, 10, add(b, b)), let(b, 20, add(a, b))) | 40 |
An expression is one of the of the following:
- Numbers: integers between Integer.MIN_VALUE and Integer.MAX_VALUE
- Variables: strings of characters, where each character is one of a-z, A-Z
- Arithmetic functions: add, sub, mult, div, each taking two arbitrary expressions as arguments. In other words, each argument may be any of the expressions on this list.
- A “let” operator for assigning values to variables: let(, , )
As with arithmetic functions, the value expression and the expression where the variable is used may be an arbitrary expression from this list.
The program uses log4j2 framework for logging. You can set the log level in the log4j2.xml file directly or using command line:
java -cp target/calculator_<version>.jar calculator.Main -l debug "let(a, 5, add(a, a))"
or
java -cp target/calculator_<version>.jar calculator.Main --logLevel info let(a, 5, add(a, a))"
Accepted values for the logLevel option are: error, warn, info, debug, or trace (case insensitive).