Determine if a string is numeric: Difference between revisions

=={{header|Z80 Assembly}}==

{{works with|CP/M 3.1|YAZE-AG-2.51.2 Z80 emulator}}

{{works with|ZSM4 macro assembler|YAZE-AG-2.51.2 Z80 emulator}}

Use the /S8 switch on the ZSM4 assembler for 8 significant characters for labels and names

<syntaxhighlight lang="z80">

;

; Check if input string is a number using Z80 assembly language

;

; Runs under CP/M 3.1 on YAZE-AG-2.51.2 Z80 emulator

; Assembled with zsm4 on same emulator/OS, uses macro capabilities of said assembler

; Created with vim under Windows

;

; 2023-04-04 Xorph

;

;

; Useful definitions

;

bdos equ 05h ; Call to CP/M BDOS function

strdel equ 6eh ; Set string delimiter

readstr equ 0ah ; Read string from console

wrtstr equ 09h ; Write string to console

nul equ 00h ; ASCII control characters

esc equ 1bh

cr equ 0dh

lf equ 0ah

cnull equ '0' ; ASCII character constants

cnine equ '9'

cminus equ '-'

cdot equ '.'

buflen equ 30h ; Length of input buffer

minbit equ 00h ; Bit 0 is used as flag for '-'

dotbit equ 01h ; Bit 1 is used as flag for '.'

;

; Macros for BDOS calls

;

setdel macro char ; Set string delimiter to char

ld c,strdel

ld e,char

call bdos

endm

print macro msg ; Output string to console

ld c,wrtstr

ld de,msg

call bdos

endm

newline macro ; Print newline

ld c,wrtstr

ld de,crlf

call bdos

endm

readln macro buf ; Read a line from input

ld c,readstr

ld de,buf

call bdos

endm

;

; =====================

; Start of main program

; =====================

;

cseg

isnum:

setdel nul ; Set string terminator to nul ('\0') - '$' is default in CP/M

print help

newline

newline

readnum:

ld b,buflen ; Clear input buffer

ld hl,bufcont

clrloop:

ld (hl),0

inc hl

djnz clrloop

readln inputbuf ; Read a line from input

newline ; Newline is discarded during input, so write one...

ld a,(inputbuf+1) ; Length of actual input

cp 0 ; If empty input, quit

ret z

ld b,a ; Loop counter for djnz instruction

ld c,0 ; Use c for flags: '-' and '.' may be encountered at most once, '-' only at start

ld hl,bufcont ; Start of actual input

loop:

ld a,(hl) ; Get next character into a

cp cminus ; Check minus sign

jr z,chkminus

cp cdot ; Check dot

jr z,chkdot

cp cnull ; Check if below '0'

jr c,notanum

cp cnine+1 ; Check if above '9'

jr nc,notanum

checknxt:

set minbit,c ; Whatever the case, no more '-' are allowed after the first character

inc hl ; Increase hl to next character and repeat until done

djnz loop

print bufcont ; If we made it this far, we are done and the string is numeric

print yesmsg

newline

newline

done:

jp readnum ; Read next input from user until terminated with ^C or empty input

ret ; Return to CP/M (unreachable code)

notanum:

print bufcont ; Print failure message

print nomsg

newline

newline

jr done

chkminus:

bit minbit,c ; If a '-' is encountered and the flag is already set, the string is not numeric

jr nz,notanum

set minbit,c ; Otherwise, set flag and check next character

jr checknxt

chkdot:

bit dotbit,c ; If a '.' is encountered and the flag is already set, the string is not numeric

jr nz,notanum

set dotbit,c ; Otherwise, set flag and check next character

jr checknxt

;

; ===================

; End of main program

; ===================

;

;

; ================

; Data definitions

; ================

;

dseg

help:

defz 'Enter numbers to check, end with empty line or ^C'

inputbuf: ; Input buffer for CP/M BDOS call

defb buflen ; Maximum possible length

defb 00h ; Returned length of actual input

bufcont:

defs buflen ; Actual input area

defb nul ; Null terminator for output, if buffer is filled completely

yesmsg:

defz ' is numeric'

nomsg:

defz ' is not numeric'

crlf: defb cr,lf,nul ; Generic newline

</syntaxhighlight>

{{out}}

<pre>

E>isnum

Enter numbers to check, end with empty line or ^C

1234

1234 is numeric

hello

hello is not numeric

12.34

12.34 is numeric

-98.76

-98.76 is numeric

4.6.76

4.6.76 is not numeric

34-56-23

34-56-23 is not numeric

-.9876543210

-.9876543210 is numeric

444555.

444555. is numeric

1234c

1234c is not numeric

123e45

123e45 is not numeric

</pre>