topic Re: Loop Parameter Reset in GDL

Loop Parameter Reset

Lingwisyer — Mon, 26 Sep 2022 20:43:17 GMT

Hi all,

If I have a loop of 1 to N utilising the parameter X=A, where A is some previously defined value, is it possible to pick out when i=G then X=B without needing to save A to a new parameter so that for other steps the original value is still utilised?

Simplified example:


!======THESE TWO LINES CANNOT BE INCLUDED IN THE LOOP======
x = 1
n = 5
!===========================================================

FOR i = 1 to n step 1

	If i = 3 then x = 5
	text2	y,	0,	x

next i

Returns:	1	1	5	5	5
Desired:	1	1	5	1	1

Ling.

EDIT: Clarified that X is outside of the loop.
EDIT 2: Wow... I am really good at manually writing out the correct return figures...

Re: Loop Parameter Reset

Barry Kelly — Tue, 08 Sep 2020 09:07:00 GMT

Just put an IF statement in your loop?
Unless I am not understanding what you need.

for i = 1 to n
X=A
if i = G then
X=B
endif
next i

Barry.

Re: Loop Parameter Reset

Lingwisyer — Tue, 08 Sep 2020 09:15:28 GMT

Doesn't that change the value of X for all proceeding steps? Or has my understanding of inline definitions been flawed this whole time... I am not up to needing this yet except for when i = N where N is the final use of that value, so a none issue, but the situation popped up into my head and made a few knots...

Ling.

EDIT : Modified original post to clarify details

Re: Loop Parameter Reset

Barry Kelly — Tue, 08 Sep 2020 09:41:08 GMT

Lingwisyer wrote:
Doesn't that change the value of X for all proceeding steps?

X can only ever equal one value.
I thought you just wanted to trap a certain count or point in the loop.

You can reset the value of X as you go through the script.
It shouldn't affect where it has been used already but will all future uses.
This is assuming you are not resetting the actual parameter value.

Whenever I change a value I always store an original version of it.

X=10
X_orig = X
X=20

Then if ever I need to go back to the original value...

X= X_orig

Maybe I don't understand exactly what you want after all.

Barry.

Re: Loop Parameter Reset

Nader Belal — Tue, 08 Sep 2020 10:17:25 GMT

Your error was in the conditional statement location



x = 1
n = 5

FOR i = 1 to n step 1
	If i = 3 then
		x = 5
	endif

	text2	y,	0,	x
next i

Re: Loop Parameter Reset

Lingwisyer — Wed, 09 Sep 2020 01:30:24 GMT

Moonlight wrote:
Your error was in the conditional statement location
x = 1
n = 5

FOR i = 1 to n step 1
	If i = 3 then
		x = 5
	endif

	text2	y,	0,	x
next i

That just shifts the number change. Does not isolate it. I will probably just end up making a new set a parameters to temporarily store the relevant values.

Ling.

Re: Loop Parameter Reset

Barry Kelly — Wed, 09 Sep 2020 01:47:14 GMT

This works if it is what you are after.

n = 5

FOR i = 1 to n step 1
	x = 1
	If i = 3 then
		x = 5
	endif

	text2	i,	0,	x
next i

Barry.

Re: Loop Parameter Reset

Lingwisyer — Wed, 09 Sep 2020 01:56:44 GMT

X is some previously defined value, external to the loop, it cannot be statically defined here.

Re: Loop Parameter Reset

Kristian Bursell — Wed, 09 Sep 2020 02:02:26 GMT

a few minor things:
1. you can do the if statement in one line without the "endif". looks better and fewer lines of code.
2. don't need the "step 1" as that is assumed unless otherwise defined

so it should read:


n = 5
for i = 1 to n
	x = 1
	If i = 3 then x = 5
	text2	i,	0,	x
next i

Re: Loop Parameter Reset

Kristian Bursell — Wed, 09 Sep 2020 02:08:48 GMT

looking back at your original post, it is as Barry said, just move the "x = 1" into the loop before the "if... x = 5".
that way its reinstating the x = 1 for each value, and it only get overwritten when the if statement is true.

Re: Loop Parameter Reset

Lingwisyer — Wed, 09 Sep 2020 03:48:06 GMT

Start of the script:

d = B - gs_fw_lower - gs_fw_upper - 2 * gs_int_fw				!Louvre space
IF louvre_over <= 0 then							!If NO louvre overlap	
		n = int(d /(gs_louvre_width - louvre_over))
		dp = gs_louvre_width - louvre_over
	ELSE
		dp = gs_louvre_thk / ( cos ( atn ( ( gs_louvre_width - louvre_over) / gs_louvre_thk) ) )
		n = int(d / dp) + 1
endIF

The loop (for one set of conditionals):

FOR i=1 to n

	...

	IF Louvred_sealside = "Both" then
		IF i = 1 | i = n then
			gs_louvre_opening_angle = gs_louvre_opening_max
			gs_louvre_width = sqr((d - (dp * (n - 1) + Louvre_over))^2 - (gs_louvre_thk)^2 ) + Louvre_over
		endIF
	endIF

	...

	cprism_ louvtopmat, louvbotmat, louvsidemat,
		5, gs_louvre_thk,
		-a / 2 + gs_fw_side_right + gs_int_fw,	-(gs_louvre_width) / 2,	_status,
		-a / 2 + gs_fw_side_right + gs_int_fw,	 (gs_louvre_width) / 2,	_status,
		 a / 2 - gs_fw_side_left - gs_int_fw,	 (gs_louvre_width) / 2,	_status,
		 a / 2 - gs_fw_side_left - gs_int_fw,	-(gs_louvre_width) / 2,	_status,
		-a / 2 + gs_fw_side_right + gs_int_fw,	-(gs_louvre_width) / 2,	-1

	...

next i

Re: Loop Parameter Reset

A_ Smith — Wed, 09 Sep 2020 07:17:10 GMT

if it's forbidden to repeat x=1 or use new parameter, n=5 like this:


FOR i = 1 to n step 1
	If i = 3 then x = 5 then
	text2	y,	0,	x
	x=1
	endif
	text2	y,	0,	x
next i

maybe if you know precisely when it occurs just exclude from the loop? (though it looks awful)
FOR i=1 to 2 ...
if i=3 then ...
FOR i=4 to n ...

Re: Loop Parameter Reset

Lingwisyer — Wed, 09 Sep 2020 07:43:20 GMT

A. wrote:
maybe if you know precisely when it occurs just exclude from the loop? (though it looks awful)
FOR i=1 to 2 ...
if i=3 then ...
FOR i=4 to n ...

Doing so would basically double the script length... Easier to just populate a half dozen new variables to my list.

Re: Loop Parameter Reset

Peter Baksa — Wed, 09 Sep 2020 08:01:50 GMT

Lingwisyer wrote:
...parameter X=A, where A is some previously defined value, is it possible to pick out when i=G then X=B without needing to save A to a new parameter so that for other steps the original value is still utilised?

You just said it:

if i = G then X = B else X = A

Re: Loop Parameter Reset

Lingwisyer — Wed, 09 Sep 2020 08:18:43 GMT

Peter wrote:

Lingwisyer wrote:
...parameter X=A, where A is some previously defined value, is it possible to pick out when i=G then X=B without needing to save A to a new parameter so that for other steps the original value is still utilised?
You just said it:
if i = G then X = B else X = A

Was hoping there would be a way that did not involve rewriting a dozen macros to use a dependent variable rather than the independent, and by the sounds of it, there is not so I will be needing to rewrite them at some point.

C = X
A = X

...

if i = G then C = B else C = A

...

*replace X with C in all dependent macros*

Sorry for looking for a lazy way out,
Ling.

Re: Loop Parameter Reset

Peter Baksa — Wed, 09 Sep 2020 11:54:40 GMT

In parameter calls you can assign variables to parameters:

call "macro" parameters A = something, ....

The subsequent calls from "macro" will use the value of something.
If you don't want to write each parameter in the call, write just the modified ones:

call "macro" parameters all, A = something