new-expressivo

This project follows Problem Set 3 of MIT 6.005, which uses ANTLR for parser generation. This system does not support additional operators such as "^", "-", and "/", and does not support "e" notation.

To compile and run the project in command line, run the following commands (assuming we are at the root directory: new-expressivo/)

javac -d bin/ -cp lib/antlr.jar src/expressivo/*.java src/expressivo/parser/*.java
cd bin
java -cp ../lib/antlr.jar:. expressivo.Main

Using the system

(Information here is copied directly from the pset assignment website)

In this system, a user can enter either an expression or a command.

An expression is a polynomial consisting of:

• + and * (for addition and multiplication)
• nonnegative numbers in decimal representation, which consist of digits and an optional decimal point (e.g. 7 and 4.2 )
• variables, which are case-sensitive nonempty sequences of letters (e.g. y and Foo )
• parentheses (for grouping)

Order of operations uses the standard PEMDAS rules.

Space characters around symbols are irrelevant and ignored, so 2.3*pi means the same as 2.3 * pi . Spaces may not occur within numbers or variables, so 2 . 3 * p i is not a valid expression.

When the user enters an expression, that expression becomes the current expression and is echoed back to the user:

> x * x * x
x*x*x

> x + x * x * y + x
x + x*x*y + x

A command starts with "!" . The command operates on the current expression, and may also update the current expression. Valid commands:

• d/d var

  produces the derivative of the current expression with respect to the variable var , and updates the current expression to that derivative

• simplify var 1 = num 1 ... var n = num n

  substitutes num i for var i in the current expression, and evaluates it to a single number if the expression contains no other variables; does not update the current expression

Entering an invalid expression or command prints an error but does not update the current expression.

To exit, type enter or return.

Example Usage (assume all of the following code are typed into one session)

> x * x * x
x*x*x

> !simplify x=2
8

> !d/dx
(x*x)+(x+x)*x

> !simplify x=0.5000
.75

> x * y
x*y

> !d/dy
x