How to select the objects in the user defined area

Short answer, yes. There are multiple ways you could approach this. One way, assuming the triangle exists as a shape in your design is to select the shape, get the polygon object from it and use the axlAddSelectPoly() function where:

axlSetFindFilter(?enabled '("noall" "shapes") ?onButtons '("shapes"))

when(axlSelect(?prompt "Select a shape.")

o_polyObj = car(axlPolyFromDB(car(axlGetSelSet())))

axlClearSelSet()

;Set the find filter to whatever you want to select within the shape, in this case let's just select all symbols

axlSetFindFilter(?enabled '("noall", "symbols"), ?onButtons '("symbols"))

axlAddSelectPoly(o_polyObj t)

l_symbols = axlGetSelSet()

axlClearSelSet()

)

At this point 'l_symbols' will contain a list of dbids of all symbols contained within that triangle.  If the triangle shape doesn't exist in the design, but you know the coordinates, you could always programmatically create the shape (either by hard-coding the coordinates or have the user draw one). Reference axlPathStart() and it's associated functions. 

axlAddSelectPoly() has some quicks though. For example if you have some additional text in your symbol definition and that text is visible when you use axlAddSelectPoly(). The function will select the symbol even if just the smallest fragment of the text is within the boundary of the shape. Because of that you might want to use axlGeoPointInShape() instead. You could select all objects in a design a check whether the objects 'xy' is within the shape using axlGeoPointInShape()

Hope this helps. 

Thank you mstaub. It should work. But i am not able to find the axlAddSelectPoly() function in allegro skill document.  i am using "17.2-2016 S070" .

is axlSubSelectPoly() function available ? if possible please share the syntax of these  functions .

You're right, I can't seem to find any documentation on it either. I'm guessing it's just an undocumented function. I am currently using it in multiple tools I wrote, so I can assure you it's working. I found one blog post saying it was introduced in Hotfix 50, so if you are on 70 you should be able to use it. 

I have the following in my notes:

axlAddSelectPoly(o_polyDbid b_include_voids)

Where:

o_polyDbid = the dbid of the poly object

b_include_voids = t: include voids in selection, nil: don't include voids in selection.

If you don't feel comfortable using that function, you can get very similar results using axlGeoPointInShape(), which is documented. 

Thankyou mstaub ! axlAddSelectPoly() function is working well..

Yes, suppose you need only symbols in the area then under find filter enable symbols. Use selection filter - select by path and draw a path (area) to select the objects.