Problem with lists

ID:145356
 
Apr 8 2006, 11:39 am
Code:
mob/var/shop = list()   
    
mob
    verb
        Shop()
            var/item = input("Select an item you would like to add to shop.","Shop") in src.contents
            var/price = input("How much would you like to sell [item] for?","Shop") as num
            shop += item
            shop += price
            var/A
            for(item in shop)       
                A ++
                world << "Item: [shop[A]], Price: [shop[A+1]]"
                A ++


Problem description:
K well It keeps on telling me that list index is out of bounds when I run the program and do the verb.. The reason probably being that it refers to shop[3] the second time it loops in the for statement . Even though it gives me this error it displays what I want it to.

I dunno why it wont let me refer to shop[3] since im adding stuff to the list that would make the list bigger then 3. Also when i tried declaring the list as mob/var/shop[20]. When it got to the for loop it displayed "Item: , Price: " 19 times before it showed the actual item and price.

Any help would be greatly appreciated.

Apr 8 2006, 3:11 pm
Well, one obvious problem here is that you're looping for(item in shop), which will literally loop through all items in the list--both objects and prices. Of course, why you didn't use an associative list, which is infinitely better, is a mystery. But be that as it may, your loop is covering the entire length of shop, and yet is incrementing A twice each time through. By the time you're done, A will be shop.length*2. As soon as A reaches shop.length or higher, you'll get a runtime error because shop[A+1] will go past the end of the list.

Solution: Use an associative list. Ditch the A var entirely.

Lummox JR
Apr 8 2006, 3:39 pm
In response to Lummox JR
Lummox JR wrote:
Well, one obvious problem here is that you're looping for(item in shop), which will literally loop through all items in the list--both objects and prices. Of course, why you didn't use an associative list, which is infinitely better, is a mystery. But be that as it may, your loop is covering the entire length of shop, and yet is incrementing A twice each time through. By the time you're done, A will be shop.length*2. As soon as A reaches shop.length or higher, you'll get a runtime error because shop[A+1] will go past the end of the list.

Solution: Use an associative list. Ditch the A var entirely.

Lummox JR

I tried reading up on associative lists and didnt quiet understand it as all I reached were problems when I tried making one. If you could show me an example of an associative list that would be very helpful.

Apr 8 2006, 3:43 pm
In response to X0Gohan0X
X0Gohan0X wrote:
I tried reading up on associative lists and didnt quiet understand it as all I reached were problems when I tried making one. If you could show me an example of an associative list that would be very helpful.

shop[item] = price

Lummox JR
Apr 8 2006, 4:16 pm
In response to Lummox JR
Lummox JR wrote:
X0Gohan0X wrote:
I tried reading up on associative lists and didnt quiet understand it as all I reached were problems when I tried making one. If you could show me an example of an associative list that would be very helpful.

shop[item] = price

Lummox JR

Thanks a bunch, I finally feel comfortable with lists now.