Spedn 0.2 released and ready for Nov 19 protocol upgrade

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Spedn is a high level smart contracts language for Bitcoin Cash. A new major version 0.2 has just been released.

This is 15th Nov 2019 hard-fork compatibility update with a bunch of changes and new features.

• Introducing an array type with syntax [type; length], for example [Sig; 3] signatures, [byte; 10] message. The compiler type-checks the lengths so for example a type of message . message expression will be inferred as [byte; 20].
• Syntax for tuple assignment now allows its items to be of different type: (int a, Sig b, PubKey c) = expr;
• Array elements can be accessed with x[i] syntax.
• Introducing a bit type. In practice only arrays of bits are useful, as they represent a type of checkbits argument in the checkMultiSig function which was upgraded for Schnorr support. Bit array literal is also introduced, ex. [bit; 5] checkbits = 0b00110.
• As mentioned - checkMultiSig accepts an additional checkbits argument, as described in Nov 15 hard-fork spec.
• For a byte array of unknown size there is [byte] type which replaces the former bin type.
• Introducing (UTF-8) string literals, ex. [byte] message = "Hello, World";.
• Introducing custom type declarations (type aliases) which can be placed before contract declarations and then used as any other type in the contract. Ex. type Message = [byte; 10];. Actually, Sig, DataSig, PubKey, Ripemd160, Sha1, Sha256, Time and TimeSpan are defined internally as aliases.
• Introducing separator; statement that compiles to OP_CODESEPARATOR.
• Introducing fail; statement that compiles to OP_RETURN.
• Introducing checkSize(x) function that returns true if the runtime size of a byte array matches the declared type.
• Variable names can now contain underscores, ex. [byte] my_string.

For developers of v0.1 there's a short migration guide which shows how to adjust an old contract code to the new syntax.