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deadlydog

Ada anyone?

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I'm working on my first Ada program, just a simple priority Queue, but I can't seem to get it working. Here's what I've got so far: (I put it in C Quotes just so that the post wouldn't be so large, seeing as how there's no ada quotes) Here's my PriorityQueue.abs file:
-- PriorityQueue.ads
-- Priority Queue Specification (Functions accessible by users)

package PriorityQueue is
   function Push(Item, Priority : Integer) return Boolean;
   function Pop(Garbage : Integer) return Integer;
end PriorityQueue;

This file compiles fine Here's my PriorityQueue.adb file:
-- PriorityQueue.adb
-- Priority Queue Implementation

package body PriorityQueue is
-- Holds a Number and its Priority
Type ItemType is
   record
   Number, Priority : Integer := -1;
end record;
type Item is array (1..100) of ItemType;

begin
   
   -- Pushes an Item into the Priority Queue
   function Push(Number, Priority : Integer) is      -- Line 15
   Index, ItemSpot : Integer := 0;
   begin
      -- Make sure Priority is valid
      if Priority < 0 then
         Priority := 0;
      end if;
      
      -- Find where to insert the new Item
      Index := 0;
      loop
         exit when Index = 101;                        -- Break out of loop if the Queue is full
         exit when Priority <= Item(Index).Priority;   -- Break out of loop if we found where to insert Item
         exit when Item(Index).Priority = -1;          -- Break out of loop if we found an empty spot
         Index := Index + 1;
      end loop;
      
      if Index = 101 then
         return false;
      end if;
      
      -- Save the spot to insert the new item in ItemSpot
      ItemSpot := Index;
      
      -- Move all Items above ItemSpot up one
      -- Start from Index = 100 and go down to Index = 1, unless an "exit" is reached
      for Index in 100..1 loop
         exit when Index = ItemSpot;      -- Exit loop once we've reached ItemSpot
         Item(Index) := Item(Index - 1);   -- Move Item up one spot in array
      end loop;
      
      -- Insert new Number and Priority
      Item(ItemSpot).Number := Number;
      Item(ItemSpot).Priority := Priority;
      
      return true;
      
   end Push;
   
   function Pop(Garbage : Integer) return Integer is
   Index, ItemNumber : Integer := 0;   
   begin
   
      -- Save Number with the lowest priority number to be returned
      ItemNumber := Item(0).Number;
   
      -- Move all Items down one spot
      for Index in 100..1 loop
         Item(Index) := Item(Index-1);
      end loop;
   
      -- Return the Number
      return ItemNumber;
   end Pop;
   
end PriorityQueue;             -- Line 70

And here are the compile errors I get while compiling PriorityQueue.adb: priorityqueue.adb:15:04: declarations must come before begin priorityqueue.adb:70:01: statement expected And here is my main file First.adb:
-- Include text_io for input/output
with text_io, PriorityQueue;
use text_io, PriorityQueue;

-- Declare "Main"
procedure First is
Index : Integer := 0;
Queue : PriorityQueue;           -- Line 8
begin
  
  Queue.Push(31, 3);             -- Line 11
  Queue.Push(4, 4);
  Queue.Push(0, 0);
  Queue.Push(51, 5);
  Queue.Push(52, 5);
  Queue.Push(7, 7);
  Queue.Push(1, 1);
  Queue.Push(6, 6);
  Queue.Push(2, 2);
  Queue.Push(32, 3);
  
  for Index in 1..10 loop
     put(Queue.Pop(Index) + "is popped off the queue");
     new_line;
  end loop;
end First;

And here's the compile errors I get with First.adb: First.adb:8:09: subtype mark required in this context First.adb:8:09: found "PriorityQueue" in priorityqueue.adb First.adb:11:03: invalid prefix in selected component "Queue" - I get one of these for each of the .Push functions. From what I understand, the .abs is like the .h in C++, and the .adb is like the .cpp, is this right? Also, can you spot some of the mistakes in my code. Thanks. [Edited by - deadlydog on October 8, 2004 11:22:35 PM]

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Quote:
Original post by Maega
It's doubtful. Ada was built for the US Government :D.

And I don't think they even use it anymore?
Anyways the only thing I know about ada is that it came up when I was learning SQL but I don't remember what the connection was?

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they use it in (some) german universities to teach the basics of programming... but i doubt ada could be used to make a graphical game... is this homework or are you actually working on an ada game?

ps: i dont know ada :/

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It is homework, but I thought since I've got all the code done and the concept down that it would be alright, seeing as how I'm only having trouble with the syntax pretty much. I've been reading through quite a few ada tutorials and it seems like it actually is a pretty cool language. It's very tight so not many errors get through at all. Maybe Windows should consider using it to code their next installment. ha :)

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Quote:
Original post by deadlydog
It is homework, but I thought since I've got all the code done and the concept down that it would be alright, seeing as how I'm only having trouble with the syntax pretty much. I've been reading through quite a few ada tutorials and it seems like it actually is a pretty cool language. It's very tight so not many errors get through at all. Maybe Windows should consider using it to code their next installment. ha :)


Ah Ada, brings back memories :D

The first file i can see that you have an extra begin at line 12, remove that. Can't spot the other errors yet (been too long), i'll dig up some very old ada code and compare to mine :D

*** EDIT: The extra begin should also get rid of the line 70 error

*** EDIT2: Oh I think i have it, you are trying to instantiate a package, which i believe acts like a 'namespace' in C/C++ so u can't do that. Create a structure for the priority queue and pass it into the functions.

something like...


TYPE PriorityQueue IS RECORD
-- variables in here (array/list, etc)
END RECORD;



HTH

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So will I need 2 files then, both the .ads and .adb, or just the .adb? Or can I simply just declare the record in my main file?

I tried switching the package to type - record like you said, and now I am getting this error on this line:

type PriorityQueue is record


Here's the error:
priorityqueue.adb:04:01: compilation unit expected


Any ideas?

Thanks for the help by the way.

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Keep the ADS and ADB files, it will be much cleaner this way (you can do it all in one file but dont)

Sorry, i didn't mean switch the package i meant add the type/record to the package which stores your array of types (move the type definition into the ads file also, might cause errors otherwise), and then declare your functions to take that record/type (Priority Queue type instance) and item to push and then return the same record out. Your functions will then operate on this record passed in and return it out again.


FUNCTION Push(PQ : PriorityQueueRecord, Item : Integer, Priority : Integer) RETURN PriorityQueueRecord;
FUNCTION Pop(PQ : PriorityQueueRecord, Item : Integer) RETURN PriorityQueueRecord;


So you could do

PQ = Push(PQ, 10, 100);

on second thought u could also use procedures (no need to return out the type or you could do operator overloading so you could just do PQ-- to pop, i think u can call push too with operator overloading, not sure how to pass the params tho :D)

Well Hope That helped, brings back memories

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At the moment my problem seems to be in referencing my array of records. When I do this:

Item(Index).Priority := -1;

I'm getting this error:

invalid prefix command in selected component "Priority"

Am I not referencing the array right? Wrong type of brackets maybe. None of the tutorials I've been reading say how to access an array of records so I'm just guessing. Thanks again for all the help so far

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