evaluate_template() and GOTO

[Mike Wilson]

Good Morning,

I am trying to direct the action to certain places in a script using variables and a consolidated GOTO command. Does anyone know why this does not work or have a suggested replacement? Thanks,
Mike W

dim tolabel as C="GOTO TEST2"

evaluate_template(tolabel)

TEST1:
UI_msg_box("test","here")

TEST2:
UI_msg_box("test","other")

[csda1]

evaluate_template knows nothing about the code environment of the invoking code (where evaluate_template is executed). It does know about the variable space, and thus can use the local variables, and anything else dimensioned with in it.

Some code like below where x carries the choice is one way to do it.

IF x=1
code test 1
ELSE IF x=2
code test 2
ELSE
default code to run (if any)
END IF

You could also set the desired code into a text string, then use evaluate_template() to run that

[Mike Wilson]

Trying to code eficiently

Ira,

I'll have to be honest that I do not understand what you wrote. This is what the Documentation says about this function, and I used this function in the code below that reads 13 fields in a table and applies these values consecutively to 13 fields in a second table, where it inserts a concatenated character string into a command line to produce a dynamic command. There is an exampe here-
http://msgboard.alphasoftware.com/al...896#post389896

Are you saying that the GOTO is not an Xbasic command? This is not too big a deal, I have several work arounds, but I was just trying to code efficiently, and if I can make a commands line dynamic with variables, I'd like to instead of many IF THEN statements.

Thanks
Mike W

Code indirection refers to the situation when you want to execute an Xbasic command that is contained in a variable (i.e. to indirectly execute an Xbasic command).

The EVALUATE_TEMPLATE(Command_String) function is used to execute an Xbasic command that is contained in Command_String.

dim tbl as p
dim global Litem as C
dim vitem as C
dim qput as C
dim objitem as C

tbl = table.open("items")
query.filter = ""
query.order = ""
query.options = ""
xi=tbl.query_create()

tbl.fetch_first()
while .not. tbl.fetch_eof()
    objitem=alltrim(tbl.itemnum)
    qitem = alltrim(tbl.item)
    Litem=alltrim(qitem)
    [COLOR="Red"]evaluate_template("Parentform:Item"+objitem+".value = "+quote(Litem))[/COLOR]
tbl.fetch_next()
end while
xi.drop()
tbl.close()

[Tom Cone Jr]

Mike,

I think Ira was saying that evaluate_template() doesn't know anything about the script in which it's running. The function can see objects and variables that exist when it's called. You're assuming the labels embedded in your script are variables. They're not. They're labels. -- tom

[csda1]

Tom,

You are correctly interpreting what I said. Any XBasic code can be part of the command string of evaluate_template() including GOTOs, but they have to GOTO labels that are also in the code of the Command string, not outside it.

But GOTO's are really a bad method. A CASE or IF...ELSE IF is generally best.

[Mike Wilson]

trying to cut corners

Tom, Ira,

Thank you very much. I believe I understand this now. Logic, and overlying paradigms of older Dos-type programming don't always mesh with what I read in documentation, try and extend from prior sucesses, and think Xbasic can (should) be able to do.

I have grunted out some great finds in efficient programming with Xbasic (and y'alls help), and am always looking for an additional less-verbose, consolidating processes. Well, this wasn't one. So be it, If-then, Case, work wonderfully, I'll type out the code and keep going.

The wisdom that you impart though this message board continuously amazes me. You are certainly both appreciated legacies...

Mike W

[Steve Wood]

Re: evaluate_template() and GOTO

Ira, I am trying to use indirection in an IF statement.

This works,

if c_tbl.foundinbase <> 1 .and. a_tbl.DISTRICT_STUDENT_ID = c_tbl.STUDENT_ID .and. a_tbl.LAST_NAME = c_tbl.LAST_NAME
...
end if

This does not (always evaluates as True)

mc = " c_tbl.foundinbase <> 1 .and. a_tbl.DISTRICT_STUDENT_ID = c_tbl.STUDENT_ID .and. a_tbl.LAST_NAME = c_tbl.LAST_NAME"
if eval(mc)
...
end if

[csda1]

Re: evaluate_template() and GOTO

Hi Steve,

It depends on the context of the eval, not necessarily having access to session, layout and global variable pointers a_tbl and c_tbl. You could dim and assign a local pointer aptr=a_tbl and bptr=b_tbl and use those local pointers instead and it may work. You can also specify the pointer space in eval() as the context, but that might have issues if you require more than one pointer space.