Cvaluate

Provides support for evaluating arbitrary C-like artithmetic/string expressions like govaluate.

Development Target

• Support basic math expression, example "1 + 1 == 2".
• Support variable in expression, example "a + 1 == 2".
• Support Accessors, example "a.b == 1".
• Support Functions in expression, example "foo(a, b)".

Development Plan

• Parse expression and get tokens.

  • Parse expression.
  • Check tokens syntax and check balance.
  • Test parse tokens.

• Build expression tree by tokens.

  • Support baisc numeric add expression 1 + 49.
  • Design expression tree like evaluationStage.
  • Test expression tree.

• Support basic math expression.

  • Support +-*/.
  • Support compare operator.
  • If two operator have same prority, like "1 + 101 % 2 * 5". Because 2 * 5 is in the right stage of operator %, so it will calculate 2 * 5 first. In this case, we will get wrong answer 2 rather than 6. This issue can be fixed by reorderStages.
  • Support bit shift.

• Support variable and accessors.

  • Support Eval(params), params is a map like name: object in gvaluate .
  • Basic data type of params is int ,float, string. Use json as base data type.
  • Support simple field accessor using json.
  • Object data of params should reload operator[] and operator for access and compare. Maybe we can accomplish it by define a base object or use template to support accessors.

• Add benchmark for Cvaluate.

• Performance enhancement.

Install Cvaluate

1. Download this repository git clone https://github.com/casbin-cpp/Cvaluate.

2. Make a directory to complie mkdir build && cd build.

3. Prepare build file cmake -DCMAKE_BUILD_TYPE=Release ...

4. Build and install make install.

Usage

void test_cvaluate() {
    using namespace std;
    string s = "1 + 2 > 1.3";
    auto expression = Cvaluate::EvaluableExpression(s);

    cout << expression.Evaluate({}) << endl;    // output true
}