Error Handling

[SteveJustin1963]

untested code probably wrong, just a lead

Adding a simple error reporting system.
Currently, when errors occur (like stack underflow or heap overflow),
MINT just silently continues or resets.

why useful:

1. Helps users understand what went wrong
2. Makes debugging user programs much easier
3. Prevents silent failures
4. Helps learning the system

could be done compactly:

; Add to error constants section
ERR_STACK:    EQU   'S'    ; Stack error
ERR_HEAP:     EQU   'H'    ; Heap overflow
ERR_SYNTAX:   EQU   'X'    ; Syntax error

; Error reporting routine - about 15 bytes
REPORT_ERROR:
    LD    A,'?'           ; Error marker
    CALL  putchar 
    LD    A,C             ; Error code in C
    CALL  putchar
    JP    ETX             ; Return to prompt

; Then modify existing error points like:
ETX1:
    LD    C,ERR_STACK    ; Stack underflow
    JP    REPORT_ERROR   ; Instead of silent continue

This would:

1. Add only about 25 bytes total
2. Provide immediate feedback
3. Make MINT much more user-friendly
4. Keep the minimal philosophy
5. Help users learn from mistakes

This enhancement:

1. Adds error reporting for:

   • Stack underflow/overflow
   • Heap overflow
   • Division by zero

2. Changes to error handling:

   Before:        After:
   ETX1:          ETX1:
   JP interpret   LD  C,ERR_STACK
                 JP  REPORT_ERROR
   

3. Error output format:

   • Shows "?" followed by error code
   • Example: "?S" for stack error
   • Then returns to MINT prompt

4. Total size impact:

   • About 60 bytes total
   • Fits easily within our 2048-byte constraint

To test try:

1 0 /     ; Should show ?D (division error)
)         ; Should show ?X (syntax error)
. . .     ; Should show ?S (stack underflow)