How does the katakana lengthening mark (長音符) sort?

Question

Usually, lists are collated using the gozyuuon order. But how does the katakana lengthening mark ー fit in?

Given the following sequence of words, what order should they be in? What are the sorting rules regarding katakana?

合格{ごうかく}
航空{こうくう}
項目{こうもく}
効力{こうりょく}
呼応{こおう}
氷{こおり}
コーナー
コーヒー
コーラー

Answer 1

According to the wiki articles 五十音順 and 日本語文字列照合順番, there is an Industrial Standard (JIS X 4061) specifying the ordering of kana, though sometimes not strictly followed.

The lengthening mark will be changed to あいうえお according to the previous kana, and ん if the previous kana is ん, and the changed word would be used in sorting. If two changed word forms are the same but the original one is different, then the one changed from the lengthening mark would come after: ああ→あー

The words you listed should be ordered as:

合格{ごうかく}
航空{こうくう}
項目{こうもく}
効力{こうりょく}
呼応{こおう}
コーナー
コーヒー
コーラー
氷{こおり}