Kernighans large earthquake problem: Difference between revisions

=={{header|68000 Assembly}}==

I'm going to make the assumption that all magnitudes are given as floating points rounded to one decimal place, e.g. "6.0" when the magnitude is exactly 6. That way I don't need to actually use floating point logic. The hardware print routines were omitted to keep things short, since the Sega Genesis doesn't have a built-in kernel and so I'd have to manually write to the video chip. Chances are you're not interested in seeing all that fluff when you'd rather look at the actual algorithm for the task.

<lang 68000devpac>;Macros

macro pushRegs 1

MOVEM.L \1,-(SP)

endm

;---------------------------------------------------------------------------

macro popRegs 1

MOVEM.L (SP)+,\1

endm

;---------------------------------------------------------------------------

macro pushLong 1

MOVE.L \1,-(SP)

endm

;---------------------------------------------------------------------------

macro popLong 1

MOVE.L (SP)+,\1

endm

;Ram Variables

ramArea equ $00FF0000

Cursor_X equ ramArea ;Ram for Cursor Xpos

Cursor_Y equ ramArea+1 ;Ram for Cursor Ypos

;cartridge header and init routine go here, I'll leave them out to keep things short. Execution falls through into here

;after the screen has been activated and the bitmap font loaded into VRAM

LEA earthquake,A3

move.l #3-1,d7 ;total line count in the file.

mainloop:

MOVE.B #'.',D0 ;find the period in each line.

MOVE.B #10,D1

jsr CharInThisLine

CMP.B #255,D0

BNE foundIt

jsr lineseek

jmp mainloop

foundIt:

;print only if magnitude is 6.1 or greater

suba.l #2,a4

cmp.b #'6',(a4)

bcs .skip

adda.l #2,a4

cmp.b #'0',(a4)

beq .skip

jsr printline

.skip:

DBRA D7,mainloop

jmp * ;end program

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; unixdict functions:

PrintLine:

MOVE.B (A3)+,D0

CMP.B #10,D0

BEQ .done

CMP.B #255,D0

BEQ .done

jsr PrintChar

bra PrintLine

.done:

ADDA.L #1,A0 ;inc past the line feed to the next word.

;fallthrough is intentional here

NewLine:

addq.b #1,(Cursor_Y) ;INC Y

clr.b (Cursor_X) ;Zero X

rts

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

IgnoreCase:

;forces lower case.

;input: d0.b

;output: d0.b

CMP.B #'A',D0 ;compare to ascii code for A

BCS .done ;if less than A, keep looping.

CMP.B #'Z'+1,D0 ;compare to ascii code for Z

BCC .done ;if greater than Z, keep looping

OR.B #%00100000,D0 ;this "magic constant" turns upper case to lower case, since they're always 32 apart.

.done

RTS

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

CharInThisLine:

pushregs d2-d4/a3

;input: d0 = char to search for. d1 = terminator of choice

MOVEQ #0,D3

.again:

MOVE.B (A3)+,D2

CMP.B D1,D2

BEQ .didntFindIt

pushlong d0

move.b d2,d0

jsr ignoreCase

move.b d0,d2

poplong d0

CMP.B D0,D2

BEQ .foundIt

addq.l #1,d3

bra .again

.didntFindIt:

MOVE.B #255,D0 ;RETURN 255 ON FAILURE

bra .exit

.foundIt:

MOVE.L D3,D0 ;RETURN ZERO-INDEXED POSITION OF CHAR ON SUCCESS

bra .exit

.exit:

move.l a3,a4

popregs d2-d4/a3

rts

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

lineseek:

;advances pointer to the "next" word without printing anything.

MOVE.B (A3)+,D0

CMP.B #10,D0

BEQ .done

CMP.B #255,D0

BEQ .done

bra lineseek

.done:

RTS</lang>

{{out}}

<pre>8/27/1883 Krakatoa 8.8

5/18/1980 MountStHelens 7.6</pre>