China DOS Union

When using SET /A for operations, if the first digit of the character is zero and the value contains 8 or 9, it will cause the value to not be read correctly.

Because except that hexadecimal has the 0x prefix and octal has the 0 prefix, the numeric value is in decimal. Therefore, 0x12 is the same as 18 and 022. Please note that octal formulas can be easily confused: 08 and 09 are invalid numbers because 8 and 9 are not valid octal digits.

Example:
C:\>set /a minute=08+5
Invalid number. Numeric constants can only be decimal (17), hexadecimal (0x11) or octal (021).
C:\>set /a minute=5+018
Invalid number. Numeric constants can only be decimal (17), hexadecimal (0x11) or octal (021).
C:\>set /a minute=0029+8
Invalid number. Numeric constants can only be decimal (17), hexadecimal (0x11) or octal (021).
C:\>set /a minute=125+09
Invalid number. Numeric constants can only be decimal (17), hexadecimal (0x11) or octal (021).

Solutions:

1. When operating constants, if the constant contains 8 or 9, do not add zero in front, in short, the highest digit cannot be zero.

Example: Incorrect (08, 009, 018, 0029)

Correct (8, 9, 18, 29)

2. Prevent the highest digit of the variable from being zero during variable operation;

Algorithm:
First take the first digit of the variable and judge whether it is zero;

If it is true, then take the remainder after the first digit and reassign it to the variable;

Execute the loop until the first digit is not zero;

Finally, use the zero-removed variable for operation.

Code:
@echo off
set mu=0001028
echo Before removing zero=%mu%
:again
if "%mu:~0,1%"=="0" (
set mu=%mu:~1%
goto again
)
echo After removing zero=%mu%
set /a num=%mu%+154
echo Operation result=%num%
pause

I encountered this problem when writing a batch script today, and finally figured out the reason.

Also found the solution, and in the future, everyone can avoid detours when encountering corresponding problems.

[ Last edited by pengfei on 2006-10-2 at 09:41 ]

Well, I didn't notice this number system

Hehe, there was a vague mention of handling when the first digit is 0 in the old posts of the forum, but I can't find that post right now.

Learning...
You can also use this algorithm to judge the number of spaces in a string.
Hehe`

Bump

Just came here again, haha...

:again
if "%mu:~0,1%"=="0" (
set mu=%mu:~1%
goto again
)

What you wrote here with :again and goto again is really cool!
It continues until the leading 0s are removed until the IF condition naturally fails and jumps out to continue executing the new content :)
Admired～～～

Inspired by the wonderful application of " :again ... goto again " from the building - owner pengfei, I tried to make a simulation experiment of recursive factorial calculation of N by learning the principle of goto of the building - owner. It is really convenient to use goto well~:)
Thank you again for the building - owner's masterpiece "Regarding the base problem in numerical operations"~:)

Calculate the factorial of N~:)
There is no boundary crossing and no illegal check, just a work for learning the application of goto of the building - owner~:)

@echo off

setlocal ENABLEDELAYEDEXPANSION



set /p n=Please enter N! ：

set /a redtek=!n!

if !n!==0 (echo The factorial of 0 is 1 && goto :Eof )



:Start



 	set /a n-=1

	if !n!==0 goto :Ok 

	set /a redtek*=n

	goto :Start



:Ok

	echo The factorial is:!redtek!

	echo The maximum can only calculate the factorial of 31, and overflow if larger~:)

:again

if "%mu:~0,1%"=="0" set mu=%mu:~1%&goto again

if 写成一行也OK

Well, this is considered the most streamlined method. Give it a thumbs up first.

The algorithm I thought of when dealing with this problem at that time was to first extract the first digit and judge whether its value is zero. This is the first step. Then how to write the code? Getting the value and judging zero are easy. Take the character in the set to get the digit, and a single IF judgment can solve it.

The second step, if there are multiple zeros, a loop and re - assignment are needed. When I thought about it, it seemed that in batch processing, the only way to implement such a loop was goto (and then I thought again whether goto would keep looping, but then I saw that the previous IF was not only a judgment of zero but also played a role in conditional judgment). Here, one IF and one goto form a complete algorithm. The code was written quickly...

[ Last edited by pengfei on 2006 - 12 - 7 at 11:58 AM ]

Here's the translation:
Here's a recursive one:

@echo off

set x=00010280

call :sub %x%

echo %y%

goto :EOF

:sub

set y=%1

if "%y:~0,1%"=="0" call :sub %y:~1%

goto :EOF

If a number starts with 0, the system considers it as octal, and since there are no 8 or 9 in octal, so an error occurs!