Arrow description for while loop

Question

This topic is continuation of https://forum.plantuml.net/12180/unable-to-add-arrow-text-description-after-backward-keyword.
I would like to ask you to add arrow description to object 'data available?'. The description back to the 'data available?' action can be executed as for elsif, i.e. (incoming description) elseif (condition) else (outgoing description).

P.S.
Could you check why dsc_5 ovrrides dsc_4?

@startuml
start
->dsc_1;
(incoming description from backward) while (data available?)
  ->dsc_2;
  :read data;
  ->dsc_3;
  :generate diagrams;
  ->dsc_4;
backward :Warning; 
->dsc_5;
endwhile
stop
@enduml

Answer 1

We are still looking for a clear syntax.

With last official release, you have to use:

@startuml
start
->dsc_1;
while (data available?)
  ->dsc_2;
  :read data;
  ->dsc_3;
  :generate diagrams;
  (->dsc_4) backward :Warning; (->dsc_5)
endwhile
->dsc_6;
:eof;
@enduml

What do you think about this one ?

Comments

I think that the '->' should be omitted to be consistent with the previously introduced syntax for (incoming description)elseif.

(->dsc_4) backward :Warning; (->dsc_5)

---

It seems that with the current implementation the while and repeat loops have different behavior / draw, i.e. without the backward keyword both loops are consistent, i.e. the intermediate arrow is present in the reverse direction.

 

If I use the backward keyword, I notice a different behavior, i.e. the repeat loop will draw an intermediate arrow after the object specified after the backward keyword while the while loop will not do that. So, the open question is whether this arrow should appear after the word backward or not. I suggest that it should not appear in both cases.

http://www.plantuml.com/plantuml/uml/TT31QWCX40RW-pp5Vuo7tDeU598yHEzbiautKbU3kjtNhoiAtKD0P9XVd8-vvSAfh8kdLX1j3-S59yk5mR_iFD-zN1K1EWbRx86XyyNcwUlDxErPWYGk0kjuJhpa4RyREfqlBamATvv-DauMkjx1XTcWHd4jgh_zC2J1jk5KAV590vJaALoWlsC4PxHk_G0L9juSNAyvE7e6Hty-N4Oze_6VXUxgWBwO9IPfmwwgGsyLlYzm57y0

@startuml
start

while (data available?)
  :read data;
->dsc_4;
  :generate diagrams;
->dsc_5;
(->inc) backward :warning; (->out)
->dsc_6;
endwhile

stop

start

repeat :foo as starting label;
  :read data;
  :generate diagrams;
-> dsc_5;
(->inc)backward:This is backward; (->out)
-> dsc_6;
repeat while (more data?)

stop
@enduml

Note that for the current implementation the '-> dsc_5' and '-> dsc_6' for the while loop and '-> dsc_6' for the repeat loop are not visible, and the compiler does not trigger any warning or error.

---

Hello all,

'->' omitted or not;
Another question/wanted feature, in order to debate :

• How to change the style (color, style) of the backward's arrows?

Hint/like:

-[#blue]->
'or
-[#green,dashed]->

Regards,
Th.

---

@wro02922

Last beta http://beta.plantuml.net/plantuml.jar takes some of your comment into account. (See here)

About '-> dsc_5' and '-> dsc_6' we should indeed trigger an error, this will be done in some future.

@The-Lu

Well, this is a good point. Maybe we should allow -> to be optional in backward, so that you can have, at user choice :

• (inc) backward:This is backward; (out)
• (->inc) backward:This is backward; (->out)
• (-[#blue]->inc) backward:This is backward; (-[#green,dashed]->out)

What do you think about it ?

---

The optional arrows seem a very tempting proposition, besides, this language syntax seems to be consistent.

---

Hello,

It's perfect like that everyone is happy there, from the optional arrows, to the definition of the style by explicitly adding the arrows...
And that is also consistent, with the general rule of PlantUML.

Thanks for yours support,
Regards,
Th.

---

It would be good to have the same approach everywhere. Will this change be applied to repeat loop and elseif?

---

Sure !

It's implemented in last beta http://beta.plantuml.net/plantuml.jar

And on the online server.

Please tell us if you find issues !

Thanks.

---

A minor problem arises if ';' is omitted from the description of the arrow.

@startuml
start
repeat :Enter data;
:Submit;
-[#blue]-> dsc_5
(-[#red]-> aaa) backward :Warning;
note right: Note
repeat while (Valid?) is (No) not (Yes)
stop

start
repeat :Enter data;
:Submit;
-[#blue]-> dsc_5;
(-[#red]-> aaa) backward :Warning;
note right: Note
repeat while (Valid?) is (No) not (Yes)
stop
@enduml

 

---

Hello PlantUML,

Here is a collateral question or an observed question, not link directly by this improvement:

• How to color the arrow after the "BB" box?
  it is good after the "CC" box: if there is another action after the box (like 'end'), but for the other...

[See on PlantUML server]

Thanks for your support,
Regards,

Th.

---

Thanks for the report !

This issue has just been fixed in last beta http://beta.plantuml.net/plantuml.jar and in the online server.

Tell us if it's not working for you.

Regards,

---

Hello PlantUML,

The issue of wro02922 with ";" or without ";" seems to be always occur.

• https://forum.plantuml.net/12211/arrow-description-for-while-loop?show=12259#c12259

@startuml
start
repeat :Enter data;
:Submit;
-[#blue]-> dsc_5
(-[#red]-> aaa) backward :Warning;
note right: Note
repeat while (Valid?) is (No) not (Yes)
stop

start
repeat :Enter data;
:Submit;
-[#blue]-> dsc_5;
(-[#red]-> aaa) backward :Warning;
note right: Note
repeat while (Valid?) is (No) not (Yes)
stop
@enduml

Regards,
Th.

---

Hello all,

In fact, if we add texts to arrow: the ';' is mandatory [-> label;]
And without label, we can omit the ';' [-[#blue]->]
Unless with backward where '(...)' replace ';'.

Regards,
Th.