A text indexer. It did case-insensitive searching, so I lowercased everything (both source text and search terms), allowing me to use a quicker substring search

A text indexer. It did case-insensitive searching, so I lowercased everything (both source text and search terms), allowing me to use a quicker substring search (i.e., no need to compare characters with case insensitivity). The indexer had to chew huge amounts of text, so the quicker the lowercasing, the better.