calcParser-himadriali

you can install this project by issuing the following command:

stack install

When installation is succesful and complete, look for the following lines:

Copied executables to /..SOME_PATH../bin:
- calcParser-exe

You should be able to call the executable:

- /..SOME_PATH../bin/calcParser-exe

Alternatively to run the program - you can also type the command:

stack run

You may view the results of our test instances we made with the command:

stack test

Input:

When running the program your input should be in the format derive(variable you are deriving in terms of, expression) for example:

derive(x, x^2)

You must use parenthesis around functions to control what is considered input such as:

derive(x, (x^2) + (2*x) + 3)

To see the reults of just our Expression parser you can first run :

stack ghci

And then 'parseTest pExpr "expression"' such as these:

parseTest pExpr "derive(x, sin(x) + (x^2))"

parseTest pExpr "(x^4) + (2 * (x^2)) + 7"

Implementation:

We have created a calculus solver with the following modules:

• Calc.hs - declares our data types. We have included instances deriving Eq which we use for our calculations and instances deriving Show which we use for printing our output.

• Parser.hs - contains our parser to take in a string and return expressions. We also include a parser for laws which are written in Laws.txt and read in at the Main.

• Implementation.hs - contains our matchFunc, our apply function, and rewrites. Here is where we match expressions to laws in order to perform the derivation.

  • We have use a special for p and q in our law handling in order to take care of constants

• Output.hs - stepList calls rewrites and doMath recursively until we can no longer rewrite the function applying the laws in order to create a list of Steps associated with a law name. The last function final is used in main to handle the error from using parse from megaParsec.

  • We also implemented simple math in the case that two constants are separated by a binary operator. It should then do the math on the constants.

• Laws.hs - includes our parsed list of laws - not necessary for running the code but could be useful for testing.

• Laws.txt - this file includes all our laws for taking derivatives which is parsed and used in the main

• Main.hs - First it takes in our law list, parses it, and creates a list of Law objects. Then it takes in an expression from stdin and parses it and then calls final on the parsed expression and prints it for the user!

• We have used several libraries and tutorials which we cite in comments- including Megaparsec

You can find our github repo here: https://github.com/himadrin/calcParser

Extra Functionality

The function simplify in Output.hs allows our app to add constants when they are left in the final solution step. You can see this in test case 6 where the derivative of 3x + 2x is 5 and in test case 7 the derivative of x^(2+3) adds them to get x^5 in the first step and then the correct final answer.

Contributors:

Winter 2020: Himadri Narasimhamurthy, Ali Hagen, assistance from Prof. Joosten and from the textbook Thinking Functionally With Haskell.

Thank you so much for your help!

Next Steps:

We would love to get this working with a web UI - unfortunately we did not have the time to do so but we are going to keep working on it!