BrainFuck part 10 - RPN calc tool

Read integers

Let's define what we want to read first

• Digits (0 to 9, codes from 48 to 57)
• Space (separator, code 32)

Our program will read numbers, space separated, and push them onto the stack

Let's start

• Memory: empty
• Cursor: first cell
• Input: space separated integers

Process

• Leave an empty space (current number on stack is null)
• While there is a char to read
  • subtract 32 and set else flag
  • if char is null : it's space
    • reset else flag, move to the right
  • otherwise
    • subtract 16 (to get the digit value)
    • add current number 10 times to current digit to get new current number
• loop

Code

>,[                     leave empty space and read char
  let's track our target values here
  space 32
  digit 48 to 57

  >++++[-<-------->]+<  subtract 32
  [                     it's a digit
    >+++[-<---->]<      subtract 16 (total 48)
    <[->++++++++++<]    add current number 10 times to current digit
    >[-<+>]             replace current number by current digit
  ]>[-                  it's space
    >                   move to next stack entry
  ]                     end of switch/case
<,]                     read char and loop

Final state

• Memory: stack of integers
• Cursor: after stack
• Input: empty (read)
• Output: unchanged

Test program

This program reads space-separated integers and then print them all as chars

>                         leave an empty cell (to go back to stack start)
>,[>++++[-<-------->]+<[  calc tool code
>+++[-<---->]<<[->++++++    ** part 2 **
++++<]>[-<+>]]>[->]<,]      ** part 3 **
<[<]>[.>]                 go back to the stack first cell and print whole stack as char