Introduction

This project is an extensible parser of simple mathematical expressions, designed as a test job for an interview.

Formatting expressions

The following text describes the rules of expression formatting when using a DefaultParser and a DefaultExpression.

• The expressions must follow the general rules for mathematical expressions.

• Two operators cannot follow each other, if you need to apply an operator to a negative number - place it in brackets.
  Examples of incorrect expressions:
  2++
2 + 2 * -1
  Examples of correct expressions:
  2 + 1
2 + 2 * (-1)
  

• The brackets will close automatically if you have not done so.
  2 * (50 - ((8 + 3) * 15 + 2 => 2 * (50 - ((8 + 3) * 15 + 2))
  

• Empty brackets are not allowed. Any brackets must contain at least one number.
  Examples of incorrect expressions:
  ()
2 - ()
  Examples of correct expressions:
  (0)
2 - (0)
  

• Floating point can be replaced by a comma.
  Examples of correct expressions:
  5.2
5,2
.2
,2
  Examples of incorrect expressions:
  1,000,000 / 100
5. * 10
  

• The multiplication sign before and after a bracket may be skipped.
  Examples of correct expressions:
  2(2 + 2) => 2 * (2 + 2)
2 / (2 + 2)2 => 2 / (2 + 2) * 2
  

• Spaces does not matter and is completely ignored by parser.
  ​ ​ ​ 2 ​ + 2 ​ => 2+2
2 3 / 2 . 3 => 23/2.3