PEP8 ask for a new input if not number

Question

I have this code that converts year input (into chari) and output it as decimal. My problem is, if by mistake, a letter or blank space is entered, the program keeps output the error message but and wont reask for a new input. Example, if ABCD is entered, it will give you the error message 4 times and exit.

Input year has to be between 1900 and 2049 (inclusive).

To reproduce the error, try with 19a0 or abcd per example.

Where am I wrong here ?

STRO    welcome,d 

entyear:STRO inptyear,d 
readnomb:NOP1                

initread:LDA     -1,i        
         STA     pos,d       
         LDA     0,i
         STA     integer,d         

readchar:LDA     0,i         
         CHARI   ascii,d     
         LDBYTEA ascii,d     
         CPA     0x000A,i  
         BREQ    exitentr    
         CPA     0x002F,i 
         BRLE    errlect     
         CPA     0x003A,i  
         BRGE    errlect     
         SUBA    48,i     
         STA     valint,d    
         LDX     pos,d       
         ADDX    1,i      
         STX     pos,d       
         BR      convint     

errlect: STRO    msgerr,d
         LDX     0,i
         STX     ascii,d   
         BR      readnomb   

multdix: LDA     integer,d   
         ASLA                 
         STA     inttemp,d   
         ASLA                
         ASLA                
         ADDA    inttemp,d   
         STA     integer,d   
         LDX     pos,d       
         SUBX    1,i         
         STX     pos,d       

convint: LDX     pos,d       
         CPX     0,i         
         BRGT    multdix     
         LDA     integer,d   
         ADDA    valint,d    
         STA     integer,d   
         BR      readchar    

exitentr:LDX     pos,d       
         CPX     0,i         
         BRLT    end         

dispint:LDA     integer,d
         CPA     datemin,i
         BRLT    errlect 
         CPA     datemax,i
         BRGT    errlect
         DECO    integer,d   
         STRO    msgspace,d
         BR      entyear
end:     STOP                


welcome:  .ASCII  "Enter a year to convert to decimal\n"
         .BYTE   0
inptyear: .ASCII  "Year ?: "
         .BYTE   0           
msgerr:  .ASCII  "\nWrong caracter detected, please enter a new year: "
         .BYTE   0           
msgspace:.WORD   0x0A0A      
         .BYTE   0                  

inttemp: .WORD   0
valint:  .WORD   0
pos:     .WORD   0
datemin: .EQUATE 1900
datemax: .EQUATE 2049
integer: .WORD   0
ascii:   .BYTE   0
         .END

score 0 · Answer 1 · answered Nov 20 '13 at 14:32

If you press enter after the digits, these: CPA 0x000A,i
BREQ exitentr
might make the program to terminate. Actually, after each invalid key the reading starts from the beginning. Unless, of course, the cherecter reading is buffered - the terminal collects the characters until newline, and then offers the whole buffer to the program to read characters from using CHARI.

I kind of guess that there is no such buffering.

PEP8 ask for a new input if not number

1 Answers1