Anything is arcane and unreadable if you don’t understand the concept behind it. As it turns out, the concept behind this, $/ join: ($- split: ‘1969–07–20’) reverse, is quite simple to understand.
In Smalltalk, characters are signified by the dollar sign. How else would you signify the slash character? ‘/’ wouldn’t work because that’s a string!
In Smalltalk, the syntax boils down to sending messages to objects. The character object $- is sent the keyword message #split:. This says use the character to split the string argument into an array. Seems very straightforward.
Next, the unary message #reverse says to reverse the order of substrings in the array.
Finally, the character object $/ is sent the keyword message #join:. This says use the character to join the array of substrings to produce a new string.
When you understand the concept behind it, it is immensely readable.