What is the best way to make a PEMDAM Calculator

[roelofw]

Hello

as my first project after watching the videos of McWorther I want to make a PEMDAM calculator.
So you can enter a calculation in the serial monitor and the end result is displayed on a LED screen.

So far no problem

But is it a good waty to use two stacks to take care that the calculations are done in the right order or is there a better way ?

[build_1971]

Do yo mean pemdas?
Why the two stacks? You really need to explain your idea better...

[roelofw]

yes. I mean that
I was thinking of 2 stacks. one for the numbers and one for the operations.

So lets say we want to solve this calculation : 2 + 3 * 8

Then I first store the 2 in the numbers stack
Then I see a + so I store it on the operations stack.
Then I see a 3 so I store it on the numbers stack
Then I see a * so I can "compare" if the * has a higher priority as the + which it has
Then I see the 8 so I can get a operation from the operations stack and a number and calculate 3 * 8 which is 24.
Then I can store the 24 in the numbers stack.
Then I can get 2 numbers from the numbers stack and a operation so I can calculate 2 + 24 = 26

Which is then the answer.
I hope this explanation is clear.

[jremington]

The best way is the way that works correctly, is easy to use and maintain, is fast, accurate and the code fits into the target processor.

[build_1971]

Ok, that makes sense.
And is doable...

[alto777]

@roelofw

in the right order

Most cheap calculators have an order. I don't call it right, but it is what it is. No stacks are involved.

If you want a useful calculator that does a better job, you might want to provide for parentheses.

a7

[DaveX]

First, I'd work through serial parsing, and then I'd skip PEMDAS and just do RPN/postfix.

@DaveX

Serial Input Basics by @Robin2

• Example 1 -- Receiving single characters.
• Example 2 -- Receive several chars with an end marker.
• Example 3 -- Receive with start- and end-markers
• Example 4 -- Receiving a single number from the Serial Monitor
• Example 5 -- Receiving and parsing several pieces of data
• Example 6 -- Program to receive binary data

How to process incoming serial data without blocking by @nickgammon

• Example 1: Non-blocking line buffering -- Non-blocking line buffering
• Example 2: Serial parsing state machine -- state-machine for parsing commands. E.g. R4500S80G3

Misc

• Serial parsing RPN/Postfix:
• pcRead by @gcjr -- one-character parsing diagnostic/control tool (w/ Simulation).
• Good Forum thread on parsing a line into tokens with strtok()
• My adaptations of @nickgammon's state-machine parser into a switch-case single-letter post-fix parser for commands and numbers. E.g. 4500R 80S 3G or '123 24 /p`:
  • V1: Simple RPN number and command parsing and
  • V2: RPN 4 function calculator+commands
  • V3: Serial control of Stepper speed, acceleration and motion control with RPN calc -- Use Serial to control a stepper with real-time adjustment of Acceleration, Maximum speed and Position, with 4-function calculator.
• txtZyme (github) with Wokwi sim of txtZyme modified for Stepper Motor

[er_name_not_found]

Use one stack to convert from infix to postfix. Then use the other stack to evaluate the postfix expression.

[westfw]

There is this old publication. ("My Dear Aunt Sally" Algorithm)
It was clear enough for me to implement it, ~45 years ago.

Byte Magazine - The Best of Byte Volume 1 : Free Download, Borrow, and...

[roelofw]

Thanks
Could be working but first study a lot to really understand things.
Will costs time but that is oke .