Updates bound.asm

This new routine:

1) Returns num of dims for both LBound(var), UBound(var)
2) Returns 0 for both LBound(var, n), Ubound(var, n) if n > num dims
3) Returns the right LBound, UBound value otherwise

Also fixes comments

Author: boriel

library-asm/bound.asm

@@ -6,18 +6,67 @@
 ; This code is released under the BSD License
 ; ---------------------------------------------------------
 
-; Implements bothe the LBOUND(array, N) and RBOUND(array, N) function
-
+; Implements both LBOUND(array, N) and UBOUND(array, N) function
 ; Parameters:
-;   HL = N (dimension)
-;   [stack - 2] -> LBound table for the var
-;   Returns entry [N] in HL
+; HL = PTR to array
+; [stack - 2] -> N (dimension)
+
+    PROC
+    LOCAL __BOUND
+    LOCAL __DIM_NOT_EXIST
+    LOCAL __CONT
+
+__LBOUND:
+    ld a, 4
+    jr __BOUND
+
+__UBOUND:
+    ld a, 6
 
 __BOUND:
+    ex de, hl       ; DE <-- Array ptr
+    pop hl          ; HL <-- Ret address
+    ex (sp), hl     ; CALLEE: HL <-- N, (SP) <-- Ret address
+    ex de, hl       ; DE <-- N, HL <-- ARRAY_PTR
+
+    push hl
+    ld c, (hl)
+    inc hl
+    ld h, (hl)
+    ld l, c         ; HL = start of dimension table (first position contains number of dimensions - 1)
+    ld c, (hl)
+    inc hl
+    ld b, (hl)
+    inc bc          ; Number of total dimensions of the array
+    pop hl          ; Recovers ARRAY PTR
+    ex af, af'      ; Saves A for later
+    ld a, d
+    or e
+    jr nz, __CONT   ; N = 0 => Return number of dimensions
+
+    ;; Return the number of dimensions of the array
+    ld h, b
+    ld l, c
+    ret
+
+__CONT:
+    dec de
+    ex af, af'      ; Recovers A (contains PTR offset)
+    ex de, hl       ; HL = N (dimension asked) - 1, DE = Array PTR
+    or a
+    sbc hl, bc      ; if no Carry => the user asked for a dimension that does not exist. Return 0
+    jr nc, __DIM_NOT_EXIST
+
+    add hl, bc      ; restores HL = (N - 1)
     add hl, hl      ; hl *= 2
-    ex de, hl
-    pop hl
-    ex (sp), hl     ; __CALLEE
+    ex de, hl       ; hl = ARRAY_PTR + 3, DE jsz = (N - 1) * 2
+    ld b, 0
+    ld c, a
+    add hl, bc      ; HL = &BOUND_PTR
+    ld a, (hl)
+    inc hl
+    ld h, (hl)
+    ld l, a         ; LD HL, (HL) => Origin of L/U Bound table
 
     add hl, de      ; hl += OFFSET __LBOUND._xxxx
     ld e, (hl)      ; de = (hl)
@@ -27,3 +76,8 @@ __BOUND:
     ex de, hl       ; hl = de => returns result in HL
     ret
 
+__DIM_NOT_EXIST:
+;   The dimension requested by the user does not exists. Return 0
+    ld hl, 0
+    ret
+    ENDP