Chapter 26 // Exercise 6 - Principles & Practice Using C++

In this exercise I'm using Visual Studio 2019 and a modified version of the std_lib_facilities header found here.

Chapter 26 // Exercise 6

Modify the calculator from Chapter 7 minimally to let it take input from a file and produce output to a file (or use your operating systems facilities for redirecting I/O). Then devise a reasonably comprehensive test for it.

Github: https://github.com/l-paz91/principles-practice/tree/master/Chapter%2026/Exercise%206

Chapter 7 is back; it's the gift that keeps on giving.

I already kind of implemented this back in Chapter 16 when we had to give this code some graphics using FLTK in C16 Exercise 9. I basically took the calculator code; did nothing to it except "fake" a cin buffer by creating an istringstream and passing the binary data directly to the cin buffer:

 string calculate(string input) 

 { 

     //put the input "into" cin 

     istringstream oss(input); 

     cin.rdbuf(oss.rdbuf());

    

     //now do normal calculator stuff as we have "characters in the buffer" 

     string answer = to_string(statement());

     //clean up token stream for next statement 

     ts.ignore(); 

     return answer; 

 }

Using this code (Exercise 9) I made it so it reads from from a text file that takes input per line, then compares it to the expected output from the next line and compares the two. I decided to just read everything in from one file instead of outputting to another file.

Amusingly, I used ChatGPT-4 to generate the test list and as I ran the tests it gave an incorrect answer for sqrt(pow(5,3)). it said it was 8.66 instead of 11.18. I've decided to leave that in so you can see a failure.