SortedCollection that ignores case in strings

Question

By default, a SortedCollection is case sensitive (which seems surprising to me given how Strings are mostly used today), e.g.,

list := #('z' 'c' 'C' 'A' 'a').
slist := list asSortedCollection. "a SortedCollection('A' 'C' 'a' 'c' 'z')"

With Spotter, I found caseInsensitiveLessOrEqual: but wasn't sure how to use it with a SortedCollection. How can I easily get a sorted collection that ignores case?

Answer 1

asSortedCollection: takes a sort block, too:

list := #('z' 'c' 'C' 'A' 'a').
slist := list asSortedCollection: 
    [ :a :b | a caseInsensitiveLessOrEqual: b ]. "a SortedCollection('a' 'A' 'C' 'c' 'z')"

Edit Here's a solution to get a consistent order (this is ugly, I got it from diving into caseInsensitiveLessOrEqual:)

caseInsensitiveCompare := [ :a :b | | result | 
    result := a compare: b caseSensitive: false.
    "equal ignoring case" 
    result = 2 ifTrue: [ a compare: b caseSensitive: true ].
    "less than, so return true (else return false since result=2)" 
    result = 1  ].

slist := list asSortedCollection: caseInsensitiveCompare. 
"a SortedCollection('A' 'a' 'C' 'c' 'z')"

Answer 2

I'm adding the answer to address @Amos M. Carpenter comment - the sorting stability. Your second code is unnecessarily complex. What you could do is add one asSortedCollection to the list (which would sort the strings based alphabet position and "capitalness" and you would get consistent solution:

list := #('z' 'c' 'C' 'A' 'a') asSortedCollection.
slist := list asSortedCollection: 
    [ :a :b | a caseInsensitiveLessOrEqual: b ]. "SortedCollection('a' 'A' 'c' 'C' 'z')"

list := #('z' 'C' 'c' 'A' 'a') asSortedCollection.
slist := list asSortedCollection: 
    [ :a :b | a caseInsensitiveLessOrEqual: b ]."SortedCollection('a' 'A' 'c' 'C' 'z')"