a light weight math expression parser library from https://github.com/codeplea/tinyexpr.

```
mkdir build && cd build
cmake ..
make
```

1. library `libtinyexpr.so` saved to `build/libs`
2. sample `tinyexpr_test` saved to `build/samples`

run sample and input math expression something like `1+2*5`, it will calculate it and output result `11`.