Blockstream developer Russell O'Connor published white paper of Simplicity, a new programming language designed to be an alternative to existing languages used to create smart contracts. It is assumed that Simplicity can be implemented over time in the bitcoin protocol via the softfork mechanism.
— Blockstream (@Blockstream) 30 октября 2017 г.
As stated in the blog Blockstream, Simplicity is based on the algorithm of sequential computation and offers several important improvements, the main one of which is the extension of the language capabilities.
One of the problems with Bitcoin Script, Bitcoin’s own programming language, is that a number of opcodes were disabled in Bitcoin’s earliest days. For example, you can add numbers in Bitcoin Script, but you can’t multiply them.
Among other important features, which Blockstream pays attention to, is an increased level of security - Simplicity is a Turing incomplete language that provides limitation of a recursive call, protection against endless cycles and allows for static code analysis.
Also Simplicity has built-in support for Merklized Abstract Syntax Trees (MAST).
All this in combination allows you to create a more secure, efficient and functional code for smart contracts.
A more detailed analysis of Simplicity is expected in the near future, while you can get acquainted with whitepaper.