Using local variables for a function which "returns" a result-CodePudding

I'm trying to use local variables in a function but it doesn't work as expected.

@echo off
setlocal

call :Sum %1, %2, sum
echo %sum%
exit /b 0

:Sum
setlocal
set "a=%~1"
set "b=%~2"
set /a "%~3=%a% %b%"
endlocal
exit /b 0

Here is the invocation of the script:

>test.bat 1 2
ECHO is off.

Any clues?

CodePudding user response：

If the expected result is to put sum of arguments into a variable then you'll need to remove setlocal/endlocal inside of :Sum.

:Sum
set "a=%~1"
set "b=%~2"
set /a "%~3=%a% %b%"
exit /b 0

Or you could try a trick from this answer Batch script make setlocal variable accessed by other batch files

Also using of commas as argument delimiters for call isn't encouraged.

CodePudding user response：

You get ECHO is off. because %sum% is not set. Here's an working example:

@echo off
SETLOCAL
CALL :Sum %1, %2, sum
ECHO %sum%
EXIT /B %ERRORLEVEL%

:Sum
SET /A "%~3 = %~1   %~2"
EXIT /B 0

CodePudding user response：

As mentioned by @montonero, the following "hack" solves the problem*:

@echo off
setlocal

call :Sum %1 %2 sum
echo %sum%
exit /b 0

:Sum
setlocal
set "a=%~1"
set "b=%~2"
endlocal & (
    set /a "%~3=%a% %b%"
)
exit /b 0

The command line endlocal & ... works due to the fact that variables are expanded before it is executed, thus creating a bridge between the local and the parent scope.

*https://stackoverflow.com/a/18291599/337149