The Awesome Factor

Here are the word names that have changed:

• find* -> find-from
• find-last* -> find-last-from
• index* -> index-from
• last-index* -> last-index-from
• subset -> filter

New shorthand words:

• 1 tail -> rest
• 1 tail-slice -> rest-slice
• swap compose -> prepose

Changes to existing word behavior:

• reverse stack effect of assoc-diff, diff
• before? after? before=? after=? are now generic
• min, max can compare more objects than before, such as timestamps
• between? can compare more objects
• <=> returns symbols

There are several motivations at work here. One is that words named foo* are a variant of foo, but otherwise the * is no help to what the word actually does differently. We’re trying to move away from word names with stars to something more meaningful.

Code with common patterns that come up a lot, like 1 tail and swap compose, is more clearly understood if these patterns are given a single name.

Factor’s subset is not equivalent to the mathematical definition of subset, so it was renamed to filter to avoid confusion. Along these same lines, diff and assoc-diff are now the more mathematically intuitive; you can think of diff like set subtraction now, seq1 seq2 diff is like seq1 - seq2.

Finally, the “UFO operator” <=> now returns symbols +lt+ +eq+ +gt+ instead of negative, zero, and positive numbers. The before? and after? words can compare anything that defines a method on this operator. Since between?, min, and max
are defined in terms of these comparison words, they also work on more objects.

Please let me know if you have any more suggestions for things words that have awkward argument orders, imprecise names, or if you can suggest alternate names for words with stars in their names.