C APIs in Extension and Extensible Languages

Scripting languages are used in conjuction with c code in two ways: as extension languages, where the interpreter is embedded as a library into an application; or as extensible languages, where the interpreter loads c code as add-on modules. these two scenarios share many similarities, as in both of them two-way communication of code and data needs to take place. however, the differences between them impose design tradeoffs that affect the c api that bridges the two languages, often making a scripting language more suitable for extending than embedding, or vice-versa. this paper discusses how these tradeoffs are handled in the apis of popular scripting languages, and the impact on their use as embedded or extensible languages.