Migration Guide

Migrating from v0.1 to v0.2

There are several syntax changes that might cause your contract compiled for v0.1 version of Spedn doesn’t compile anymore. Here’s how to fix it:

  1. The bin type has been replced by [byte]. Just replace all occurences. This will be good enough but consider being more strict by providing the exact size of the byte array, like [byte;5].

  2. Tuple destructuring has a new syntax. Instead of bin [a, b], use ([byte] a, [byte] b). As before, consider being more strict, ex. ([byte;4] a, [byte;28] b).

  3. With the November 2019 BCH protcol upgrade, OP_CHECKMULTISIG started to support Schnorr signatures but using this requires providing a checkbits argument instead of null dummy. Spedn 0.2 supports this mode exclusively so you’ll have to add a checkbits argument.


    challenge(Sig a, Sig b) {
        verify checkMultiSig([a, b], [k1, k2, k3]);


    challenge([bit;3] checkbits, Sig a, Sig b) {
        verify checkMultiSig(checkbits, [a, b], [k1, k2, k3]);
  4. A single code file can now contain multiple contracts therefore the compiler in Spedn TypeScript SDK returns a new data structure called module instead of a single contract template. Instead of const MyContract = await compiler.compileFile("./MyContract.spedn"); use const { MyContract } = await compiler.compileFile("./MyContract.spedn");.