unique for a block doesn't remove duplicates

Question

The strings are part of urls of which I stripped out the base. parse detects four urls in some html file. I've narrowed down the problem to this:

REBOL []
images: [{,W,H,wi,1TV1Rvu8EF9FDdUxKy+hTKK/RNifw3WQDJEI/sYkX78tyNifGd0/U4RpaBox1rO448B4dv24sYoTgxOMVC7Lz5J9sJXlk0nkM89n55HzX7qbRiX/cSkd3lepAEIj3LVTN7gmQLCI2+INwwg18IyDklZ3VZWkw011+77dkfgTTRlRaY397ricx4dk4BTHvCLZ} {,W,H,wi,1TV1Rvu8EF9FDdUxKy+hTKK/RNifw3WQDJEI/sYkX78tyNifGd0/U4RpaBox1rO448B4dv24sYoTgxOMVC7Lz5J9sJXlk0nkM89n55HzX7qbRiX/cSkd3lepAEIj3LVTN7gmQLCI2+INwwg18IyDklZ3VZWkw011+77dkfgTTRlRaY397ricx4dk4BTHvCLZ} {,W,H,wi,1TV1Rvu8EF9FDdUxKy+hTKK/RNifw3WQDJEI/sYkX78wvYn3cKtEeN/9Y8EfNR8J48B4dv24sYoTgxOMVC7Lz5J9sJXlk0nkM89n55HzX7qbRiX/cSkd3lepAEIj3LVTN7gmQLCI2+INwwg18IyDklZ3VZWkw011+77dkfgTTRlRaY397ricx4dk4BTHvCLZ} {,W,H,wi,1TV1Rvu8EF9FDdUxKy+hTKK/RNifw3WQDJEI/sYkX78wvYn3cKtEeN/9Y8EfNR8J48B4dv24sYoTgxOMVC7Lz5J9sJXlk0nkM89n55HzX7qbRiX/cSkd3lepAEIj3LVTN7gmQLCI2+INwwg18IyDklZ3VZWkw011+77dkfgTTRlRaY397ricx4dk4BTHvCLZ}]

print join "before: " length? images
unique images
print join "after: " length? images

print join "1=2? " images/1 = images/2
print join "1=3? " images/1 = images/3
print join "1=4? " images/1 = images/4
print join "2=3? " images/2 = images/3
print join "2=4? " images/2 = images/4
print join "3=4? " images/3 = images/4

As can be seen, urls 1 and 2 are identical, and the same can be said to urls 3 and 4. Still, unique doesn't remove the duplicates. Why does this happen, how to deal with it?

I think that if something modifies, it should be a verb. There are some violations, like **exclude** and **intersect** do not modify. *(In that case, I'd think that exclude should probably modify, but intersect should be renamed to "intersection")* — HostileFork says dont trust SE, Jul 24 '15 at 12:16

score 4 · Accepted Answer · answered Jul 24 '15 at 12:09

4

UNIQUE does not modify original series. Whether function modifies is usually mentioned in it's help string, see SORT for example. Just set your block to the result of UNIQUE, like this:

>> a: [1 2 3 4 3 4 4] 
== [1 2 3 4 3 4 4]
>> unique a           
== [1 2 3 4]
>> a                  
== [1 2 3 4 3 4 4]
>> a: unique a          
== [1 2 3 4]
>> a
== [1 2 3 4]

answered Jul 24 '15 at 12:09

rebolek

1,281
7
16

I must have confounded the modify/not modify with `sort` or other word. Thanks. – Luis Jul 24 '15 at 13:32
It's always safer to expect that function does not modify and assign the result. – rebolek Jul 25 '15 at 18:43

unique for a block doesn't remove duplicates

1 Answers1