Lambda the Ultimate

Roberto Ierusalimschy, Luiz Henrique de Figueiredo, and Waldemar Celes, "Passing a Language through the Eye of a Needle: How the embeddability of Lua impacted its design", ACM Queue vol. 9, no. 5, May 2011.

A key feature of a scripting language is its ability to integrate with a system language. This integration takes two main forms: extending and embedding. In the first form, you extend the scripting language with libraries and functions written in the system language and write your main program in the scripting language. In the second form, you embed the scripting language in a host program (written in the system language) so that the host can run scripts and call functions defined in the scripts; the main program is the host program.
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In this article we discuss how embeddability can impact the design of a language, and in particular how it impacted the design of Lua from day one. Lua is a scripting language with a particularly strong emphasis on embeddability. It has been embedded in a wide range of applications and is a leading language for scripting games.

An interesting discussion of some of the considerations that go into supporting embeddability. The design of a language clearly has an influence over the API it supports, but conversely the design of an API can have a lot of influence over the design of the language.