Typed value #244
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Typed value #244
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This is very old debugging code that shouldn't be there any longer.
This trait lets Boolean iterators collect their bits. Simplicity values have a compact and a padded bit encoding, so there will be two bit iterators. BitCollector gives both iterators collection functionality, without us defining four collection methods for two iterators. Temporarily add #[allow(dead_code)] so the diff of the coming commits becomes smaller.
It helps to have dedicated constructors for each word type, so users of the API don't have to compute 2^n in their head.
Values have two bit encodings: 1) Compact: witness encoding, IMR computation 2) Padded: values on the Bit Machine The code so far used the compact encoding exclusively, which is incorrect for sum values on the Bit Machine. As a fix, this commit introduces the padded encoding. However, a value can only be encoded with padding if its type is known. To this end, this commit refactors the Value struct so it knows its Simplicity type. Adding types to all values instead of "upgrading" a typeless value to a typed value has several benefits: 1) Bit words, products and options get their type for free when they are constructed. The caller doesn't have to supply additional type info. This covers almost all values that we are using in the code. 2) Values cannot be decoded without type info. Type checking happens implicitly during decoding. The decoded value gets its type for free. 3) Values are used as word constants and as witness data. In both cases, we want to check if the supplied value is of the correct type. There is (almost?) no use case for untyped values. The new API exposes two Boolean iterators (iter_compact / iter_padded) instead of do_each_bit. The iterators are more flexible and can be used in conjunction with BitCollector. Most changes in this commit happen inside value.rs. The rest is renamings of Arc<Value> to Value, etc.
Use from_byte_array when possible. This should be faster than a deep recursion into ever smaller Value constructors. The code is also more concise. Update documentation.
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69d3e51 fix: Export BitCollector (Christian Lewe) Pull request description: This tiny PR adds an export that I forgot in #244. It turns out that I need this export. ACKs for top commit: apoelstra: ACK 69d3e51 successfully ran local tests; SGTM Tree-SHA512: 9502cbbebe3939a99d7689cf1bba8fe11c1050886d6a4cf5ef61748812be864344dc117592da597157309b0b68918b63d805eda5918cc950dc84cc68f0b389cc
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We need to encode values with padding on the Bit Machine. This encoding requires information about the type of the value. It turns out that universally typing all Simplicity values produces the smallest diff, and it is the safest API. This PR refactors the
Valuestruct to include type information.I also have ideas for a
Wordstruct that wraps values of the word type. Only these values are safe to use in word jets. I will leave this for a follow-up PR.