Declined Multi-line UDFs

[vefatica]

Multi-line user-defined functions would be nice ... perhaps in libraries (?).

@my_function {
rem commands
rem ...
rem need a way to specify the value of the function call
}

Here's a rather clumsy way of using a library function (or alias?, or BTM?) to mimmick a UDF without any temp files. These aren't the best of examples but I hope they make a point.

v:\> function udf
%@exec[@%$]%_this

v:\> library /f factorial
factorial {
set _this=1
do i=2 to %1
set /a _this*=%i
enddo
}

v:\> library /f ncr
ncr {
set _this=%@eval[%@udf[factorial %1] / %@udf[factorial %2] / %@udf[factorial %@eval[%1-%2]]]
}

v:\> echo %@udf[factorial 7]
5040

v:\> echo %@udf[ncr 6 2]
15

 

[samintz]

I'm not understanding. What's different between a FUNCTION and a LIBRARY function? Why is one more advantageous over the other?

 

[vefatica]

I'm not understanding. What's different between a FUNCTION and a LIBRARY function? Why is one more advantageous over the other?

I think "library function" is unfortunate terminology. To me, the things currently usable in libraries are more like aliases (of even BTM files) ... they don't "have values" ... they do things. A function is an expression (like %@inc[5]) that is automatically replaced by its value.

 

[samintz]

Ahh. I get it. You want to be able to use a "library function" in an expression instead of as a command. Did you want the definition to be multi-line or the invocation to be multi-line or both? e.g.

function  myfunc = {
...
}
echo @myfunc(
...
)

 

[samintz]

I did this fairly easily:

library /f factorial
factorial {
setlocal
set _this=1
do i=2 to %1
  set /a _this*=%i
enddo
echo %_this
endlocal
}
function factorial=`%@execstr[factorial %1]`

factorial 6
720

echo %@factorial[6]
720

 

[vefatica]

Ahh. I get it. You want to be able to use a "library function" in an expression instead of as a command. Did you want the definition to be multi-line or the invocation to be multi-line or both?

I want the definition to be multi-line. That can't be done now without jumping through some hoops.

 

[vefatica]

I'm trying to avoid @EXECSTR and its temp files.

 

[vefatica]

See what a difference @EXECSTR makes:

v:\> function factorial
%@execstr[factorial %1]

v:\> library /f factorial
factorial {
set _this=1
do i=2 to %1
set /a _this*=%i
enddo
echo %_this
}

v:\> timer & do i=1 to 1000 ( echo %@factorial[6] > nul ) & timer
Timer 1 on: 17:02:52
Timer 1 off: 17:03:23  Elapsed: 0:00:31.25

v:\> function factorial
%@exec[@factorial %1]%_this

v:\> library /f factorial
factorial {
set _this=1
do i=2 to %1
set /a _this*=%i
enddo
}

v:\> timer & do i=1 to 1000 ( echo %@factorial[6] > nul ) & timer
Timer 1 on: 17:08:12
Timer 1 off: 17:08:14  Elapsed: 0:00:01.84

 

[samintz]

That's a pretty substantial difference. How does the function delay the expansion of %_this?

 

[vefatica]

That's a pretty substantial difference. How does the function delay the expansion of %_this?

That's just normal behavior. There are two expressions in %@exec[@factorial %1]%_this ... evaluated left to right. After %@exec[@factorial %1] is evaluated (empty string), _this is set.

 

[samintz]

That's a clever hack too. But to your original point, you need 3 things to make it work:
1) A library function or BTM file
2) a FUNCTION that invokes the LIBRARY function
3) a variable that holds the output of the LIBRARY function.

 

[vefatica]

That's a clever hack too. But to your original point, you need 3 things to make it work:
1) A library function or BTM file
2) a FUNCTION that invokes the LIBRARY function
3) a variable that holds the output of the LIBRARY function.

Yup, it was just a hack. I'd like more elegant support for multi-line user-defined functions. It seems a reasonable enhancement of the library mechanism.