Using a variable as direction for GOTO statement

[Mike Wilson]

Does anyone know if/how a variable can be used with a GOTO command? I'm trying to give the user choices in a List dialog to filter a table based various date groups (last week, yesterday, today, tomarrow, current week, next week) and have this choice in a variable direct to a LABEL where the filter would reside. This is likely not possible and I'll probably have to go through a SELECT-CASE series, but I thought I would ask first. A test example that doesn't work is below.

dim vCH as C = "TWO"
dim vto as C

vto = "GOTO  L" + vCH

Evaluate_template(vto)

LONE:
MSGBOX("AT ONE", vto)

LTWO:
MSGBOX("AT TWO",vto)

LTHREE:
MSGBOX("AT THREE",vto)

[Stan Mathews]

Re: Using a variable as direction for GOTO statement

Mike,

The issue is not constructing a GOTO statement using a variable. I'm not sure if it should work or not but it seems that any use of evaluate_template() that affects the flow of the script is ignored. Statements that affect other objects are executed.

Try this and note that the END command supplied in the variable is ignored.

debug(1)

dim vCH as C = "LTWO"
dim vto as C

'vto = "GOTO " + vCH
vto = "END"

evaluate_template(vto)
MSGBOX("AT ONE", vto)
end 

LONE:
MSGBOX("AT ONE", vto)
resume next

LTWO:
MSGBOX("AT TWO",vto)
resume next

LTHREE:
MSGBOX("AT THREE",vto)
resume next

[Tom Cone Jr]

Re: Using a variable as direction for GOTO statement

In limited testing here it seems that the GOTO statement requires an actual labelname as its argument. If the labelname is in a variable GOTO will interpret the variablename as the labelname and throw an error. The variable is not evaluated, nor is the labelname substituted for the variable at runtime.

[Mike Wilson]

Re: Using a variable as direction for GOTO statement

Thanks Tom,

I'm seeing you are correct. I've wanted this for a long time. OK, I will put this to rest and just use if-then or select-case sequences. It works fine, but just ends up being more coding.

[csda1]

Re: Using a variable as direction for GOTO statement

Hi Mike,

When using the evaluate_template, it can't locate any goto labels that are not included in it's arguments.

If you set a variable to the evaluate_template(), you'll see that that variable will return the error for the evaluate_template. The code for the evaluate_template() must have it's own internal error handler if desired.

So when using evaluate_template, use it like this

result=evaluate_template(code_in_variable)
IF .not.(result=="")
' result contains text error, e.g. "Can't locate that symbol" for your case
end if

[Mike Wilson]

Re: Using a variable as direction for GOTO statement

Ira,
Sorry, but you lost me.

I'm not trying to error trap an evaluate_template() result, I'm trying to use a variable as the LABEL NAME for the GOTO statement in xbasic script. Possible?

dim vLabel as C = "TESTLABEL"

GOTO var->vLabel
END

TESTLABEL:
msgbox("made it here")

[csda1]

Re: Using a variable as direction for GOTO statement

Hi Mike,

All goto and labels have to be in the variable that is used in the evaluate_template input, as in

dim vCH as C = "TWO"
dim vto as C

vto ="GOTO  L" + vCH+crlf()+<<%code%

LONE:
MSGBOX("AT ONE", vch)
end

LTWO:
MSGBOX("AT TWO",vch)
end 

LTHREE:
MSGBOX("AT THREE",vch)

%code%

' notice that vto is just one long string 
' with multiple lines of code
rslt=Evaluate_template(vto)

[Mike Wilson]

Re: Using a variable as direction for GOTO statement

Ira,

Thank you very much for explaining that. So, OK, no way is evaluate_template going to work for me since some of my scripts have numerous episodes of List-List dialog for user choices throughout the script and many sequences of direction and re-direct. The code-within-code-within-code would be unresolvable, at least to this man. I'll stick with what's working, albeit needing more coding, and ask for something more simple as a wishlist.

Thanks again.

[Tim Kiebert]

Re: Using a variable as direction for GOTO statement

Hi Mike,

Not sure if this will result in any less coding in your context than a select-case structure but does make code quite flexible. I think you can do without the local_variables if you make the variables in the main script shared but include it here just for the example. Hopefully Ira will comment and correct any errors.

dim vCH as C = "two"
dim  vto as C = "xxx"
dim vl as p

vl = local_variables()

Evaluate_template(vch+"(vl)")


FUNCTION one as V(vl as p)
    with vl
    MSGBOX("AT ONE",vto)
    end with
END FUNCTION


FUNCTION two as V(vl as p)
    with vl
    MSGBOX("AT TWO",vto)
    end with
END FUNCTION


FUNCTION three as V(vl as p)
    with vl
    MSGBOX("AT THREE",vto)
    end with
END FUNCTION

[Mike Wilson]

Re: Using a variable as direction for GOTO statement

Tim,
Quite interesting! It replaces LABEL segments with Function segments. I'll keep this in mind, for sure. Thanks!

[Tim Kiebert]

Re: Using a variable as direction for GOTO statement

Mike,

I had this old thread in the back of my mind re using functions instead of goto. I don't think I have used a goto since reading it.

[Mike Wilson]

Re: Using a variable as direction for GOTO statement

Tim,
Thank you for that link. It will take me a while to digest all that as it contains some pretty high level understandings that don't immediately jump off the page to me. I'm not immediately seeing how I would replace all the GOTO processes I use with this approach, but I'm going to work on it, as I am sensing making that transition will enrich my current level of scripting knowledge and efficiency.

One thing is pretty certain though, is that my wishlist item for a function to use a variable as a label pointer for GOTO statements isn't going to get much consideration from those that consider GOTO as not having much purpose and working to replace it's utility, huh?

[Al Buchholz]

Re: Using a variable as direction for GOTO statement

One thing is pretty certain though, is that my wishlist item for a function to use a variable as a label pointer for GOTO statements isn't going to get much consideration from those that consider GOTO as not having much purpose and working to replace it's utility, huh?

As Bill Murray so apply put in "Stripes", "That's a fact, Jack!"... ie yes, use the functions method as described. Sometimes we like to use our own way of doing things instead of the way of the programming model. Those that fight the model suffer long and hard battles that they likely lose. You have made a wise choice, grasshopper... (Someone back a long ways a go said that....)

[csda1]

Re: Using a variable as direction for GOTO statement

Hi Mike,

As Al said, your wish list request will never happen. There is really no use I can imagine that would be better served by your desired method. But let's go back to your original problem that you are trying to accomplish.

I'm trying to give the user choices in a List dialog to filter a table based various date groups (last week, yesterday, today, tomarrow, current week, next week) and have this choice in a variable direct to a LABEL where the filter would reside. This is likely not possible and I'll probably have to go through a SELECT-CASE series, but I thought I would ask first. A test example that doesn't work is below.

From the above, it sound like that you have a list of items that you want to select the corresponding filter to the selected item. This is just a matter of getting the list position of 1, and then returning the list item 2. This is accomplished simply and has more expandability something like this:

list1=<<%text%
red
white
blue
green
orange
%text%

list2=<<%text%
filter 1
filter 2
filter 3
filter 4
filter 5
%text%

selected="blue"

filter_selected=word(list2,wordat(selected,list1,crlf()),crlf())

ui_msg_box("Select Result","Select:"+selected+crlf()+"Filter:"+filter_selected)
end

A similar method can also be done with arrays instead of lists.

[dik_coleman]

Re: Using a variable as direction for GOTO statement

There is one more little 'facet' about goto labels.....
If you are using XDialog with %dlg% ... some code ....%dlg%,%code% .... and try to use a goto command within the %code% section ---- the label MUST ALSO BE within the %code% section. Then if some other action is required once you leave the %code% section, you can assign a value to a variable or flag before you leave the section. Alpha cannot see outside the XDialog segments. It is really not a problem once you find this out and write your code appropriately. Using a goto label is one way to quickly exit from select clauses without having to process all of the clauses.

D

%dlg%
......
%dlg%,%code%
if a_dlg_button= "OK" then
goto area1
end if
...
..
...
...
area1:

%code%

.....
etc