[silentbicycle]

The whole s/X/Y/ thing is very Unix, and is a (sub)cultural signifier as much as anything. I'm not sure if it's originally from ed, sed, or what, but most people (self included) probably picked it up from vi (nvi/vim/etc.) or perl.

X->Y makes just as much sense, but the s (for "substitute") makes it mnemonic - I read it as "sub X for Y".

[aaronblohowiak]

ed gave rise to sed and vi. ed -> em -> ex (VIsual mode). vim is Vi iMproved.

x->y suggests lambda to many people in our community.

Edit: I meant to provide some additional information to other readers, not to disagree in any way.

[silentbicycle]

Well, right, but how many people here have actually used ed standalone? (lone hand) It's overwhelmingly likely that most people picked it up from vi(m).