I did exactly that in TXR Lisp, after initially following the Common Lisp naming. In the same change, I also made a function called shuffle nondestructive, and

I did exactly that in TXR Lisp, after initially following the Common Lisp naming. In the same change, I also made a function called shuffle nondestructive, and introduced nshuffle. It's a backwards compat breakage, but there is a mechanism in the language which helps with such situations. txr -C 237 or setting the TXR_COMPAT environment variable to 237 or lower will restore the destructive behavior of sort and shuffle. People who don't want to fix their code can deploy that way. I hate compatibility breaking changes, but it was a real thorn in my side how sort is destructive without any indication in its name, in a language where destructive versions of functions should be separately named. Now the thing is that sort is not required to be destructive. It is allowed to be. Therefore code written to the language spec will not break if sort becomes pure. But we have to worry about breaking all programs though, not just programs written to the spec. (Unless we are GCC maintainers; different rules apply.) You can't just say, "Oh, programs that call sort on a vector and ignore the return value, expecting the vector to be sorted, are just nonportable junk; let them break."