Skill - access to pins List

One tip, look at each API what the possible return values are. This will save you a lot of headaches...  Most of them you can find back in the Allegro SKILL Reference document. (see help documents)

From the API description of axlGetSelSet() :

lo_dbid List of figure dbids.
nil Select set is empty.

So it always returns a list when something is selected. Even in the case if only 1 item is selected.

Each entry in 'symb = axlGetSelSet()'  is a symbol database ID. This symbol ID contains a list, a so called disembodied property list (DPL). This is basically a list of names and values.  For example a name in the Allegro symbol DPL is 'pins'. You can find all entries in the 'The Allegro PCB Editor Database User Model'  chapter in Allegro SKILL Reference documentation.

A basic LISP operation to get the 1st element of a list is car()

With the '->'  you can access a variable inside a DPL  It returns a single item which can be any valid variable type (list, float, string, etc)

With '~>'  iterates over a list of items and tries to return the value of the given name. It returns a list containing the values which are inside the requested name

So;

symbols = axlGetSelSet()   returns a list of selected symbol(s)

symb = car(symbols)  ; get first item from list

pins = symb->pins ; is a list of pins. Each pin is a database ID. So the list looks like this: (dbid1 dbid2 dbidn)

length(symb->pins)  ; returns pin count, same as length(pins) since 'pins' was set to symb->pins

By using symbols~>pins  you will get a list containing lists of pins.  If there was only 1 symbol selected then the length(symbols~>pins) returns 1, since there is only 1 'pin list'

Do you want to iterate over all symbols:

foreach(symb symbols

 pins = symb->pins

 println(length(pins))

)

symb2 = nth(100 allDBids~>components)
length(symb2~>pins) -> RETURNS THE CORRECT AMOUNT OF PINS

This is because you assigned symb2 to the 100th item in the list of symbols. The ~> instead of -> in this case is working since the 'pins' itself is a list.  However i suggest not to use ~> in any case, unless you are certain that you can not do without it.

Some small exercise:

axlDBGetDesign()->components                  Returns a list of component dbids
axlDBGetDesign()->components->pins             does not work. There is no single 'pins' property name inside the list of components.
axlDBGetDesign()->components->pins~>number  Same as above, component->pins returns nil, so no single 'number' property can be accessed.
axlDBGetDesign()->components~>pins->number  does not work. list with pin lists does not have a single property name 'number'
axlDBGetDesign()->components~>pins~>number  returns a list with lists of pin numbers

Difference between ->components and ->symbols:

axlDBGetDesign()->components  contains all component instances imported from the netlist. No physical data like location, rotation etc.

axlDBGetDesign()->symbols contains all placed symbols instances in the PCB, so also the location, rotation etc.

Thank you for taking the time to reply !
OK, it now makes sense that I only have one item in the first code : axlGetSelSet doesn't return the object selected, but a list of objects ; in this case, a list with 1 element... That is clear now.

You mention the chapter "The Allegro PCB Editor Database User Model" in Allegro SKILL Reference documentation. May I ask where I could find this document ? In Allegro's installation directory, there are a few documents but none of them has that chapter, and when I search the web, I mostly find the same documents, plus some other about functions that are only working within Virtuoso or with Framework II (not sure what that on is).

B Bruekers said:

With the '->'  you can access a variable inside a DPL  It returns a single item which can be any valid variable type (list, float, string, etc)

With '~>'  iterates over a list of items and tries to return the value of the given name. It returns a list containing the values which are inside the requested name

Ok so -> gives you access to what we could compare to a "pointer" in C whereas ~> only gives you the value of the item, but is not linked to it directly ? Or am I completely wrong ?

Anyway, I rearranged the code to something that looks more like what you wrote and now -> works ! I am not sure exactly why but it is already a good step :p

Thank you a lot for the exercises, I will try fiddling around with those tomorrow morning.

Thank you for taking the time to reply !
OK, it now makes sense that I only have one item in the first code : axlGetSelSet doesn't return the object selected, but a list of objects ; in this case, a list with 1 element... That is clear now.

You mention the chapter "The Allegro PCB Editor Database User Model" in Allegro SKILL Reference documentation. May I ask where I could find this document ? In Allegro's installation directory, there are a few documents but none of them has that chapter, and when I search the web, I mostly find the same documents, plus some other about functions that are only working within Virtuoso or with Framework II (not sure what that on is).

B Bruekers said:

With the '->'  you can access a variable inside a DPL  It returns a single item which can be any valid variable type (list, float, string, etc)

With '~>'  iterates over a list of items and tries to return the value of the given name. It returns a list containing the values which are inside the requested name

Ok so -> gives you access to what we could compare to a "pointer" in C whereas ~> only gives you the value of the item, but is not linked to it directly ? Or am I completely wrong ?

Anyway, I rearranged the code to something that looks more like what you wrote and now -> works ! I am not sure exactly why but it is already a good step :p

Thank you a lot for the exercises, I will try fiddling around with those tomorrow morning.