This is a REPL calculator in the style of PostScript. The purpose of this project is to practice TypeScript.
Requires node v11 or higher.
Run npm install and then npm run build. The transpiled JavaScript will be placed in /dist/.
Start the program with npm run start. The REPL prompt will appear with => . Exit with <ctrl> + c.
There is a single stack that holds the state of the calculator. Each new number or operation pushes to the stack and executes. When <enter> is pressed, the stack is printed, with the top of the stack printed first. The stack persists across prompts, but not REPL sessions.
Example:
=> 1 2 3
3
2
1
=> +
5
1
Operations are applied in Postfix Notation from the top of the stack. This notation removes the need for operator precedence and parenthesis tracking.
Binary operators consume the two top elements of the stack and push the result of the operation back onto the stack.
Example:
=> 1 2 +
3
=> 4 -
-1
=> 6 * -3 /
2
| Operator | Operation |
|---|---|
| + | add |
| - | subtract |
| * | multiply |
| / | divide |
| % | mod (remainder) |
Commands do not add a result back onto the stack.
| Command | Inputs | Result |
|---|---|---|
clear |
0 | Clears the stack |
pop |
0 | Pop the top element from the stack |
swap |
0 | Swap the top two elements on the stack |
def |
2 | Define a variable, with the identifier being the top-most element |
Variables are defined with <value> /<identifier> def. Variables are evaulated immediately when their identifier is pushed to the stack.
=> 2 3 +
5
=> 3 /x def
5
=> 2 x *
6
5
=> -
-1
=> clear
=> 4 5 + 3
3
9
=> pop
9