# Language changes that possibly break old answers?

I've seen some code golf languages that still a work in progress (functions being added etc), but they have already been made public and people are posting answers using those languages.

I'd like to know what the standard practice is regarding changes to the language as it's still being polished. Adding functionality is always fine (with the usual restriction for not winning challenges with a posterior version of the language). But what about changing functionality? That would imply old answers would possibly cease to work in the new version. Is that considered acceptable? Should the language designer ensure full backwards compatibility?

As a specific example, suppose a language has function Xo for producing the number pi.1 Later on, the designer decides the name Xo would be better suited for a new function that is going to be introduced. To what extent would it be acceptable to rename the function that produces pi, and change the meaning of Xo? "Never do that" / "Try to avoid it as much as possible" / "Only in some cases" / "Don't worry, that happens all the time"... ?

1o looks like a circle, and X is an extension prefix

• The extent to which you choose to make your language backwards-compatible is a private matter between you and your language users, not an issue which affects the running of PPCG. Dec 15, 2015 at 12:48
• I wouldn't call that "private" when the language is made public. And I think the question does affect PPCG, that's why I asked here. Sorry if it's off-topic, though Dec 15, 2015 at 12:57