Clarification on false value in Script

Question

From my interpretation of the bitcoin Script Wiki and the rust-bitcoin codebase, two items on the stack get interpreted by bitcoin Script as false:

1. The empty array []
2. The single byte 0x00

Q1: Is it correct to think that a 2-byte long or more array of 0s (even though as a number would get interpreted as 0) would not be interpreted by bitcoin Script as false? For example the script OP_PUSHBYTES_4 <0x00000000> would put a byte array of 0s on the stack but still equate to true? On the other hand the script OP_PUSHBYTES_1 <0x00> would interpret as false?

Q2: Will an opcode like OP_NOT work with/interpret both of the above as false? (the docs on rust-bitcoin, Push 1 if the top item is zero; otherwise, push 0. are not very explicit in that sense, and the bitcoin wiki is even worse).

Answer 1

For the purposes of determining whether a Script stack element is true/false in boolean context:

• The empty array is false (the canonical encoding of the number 0).
• Any array consisting of just 0x00 bytes is false (an overly long, but still valid encoding of the number 0).
• Any array consisting of just 0x00 bytes, followed by a single 0x80 at the end, is false (encodings of "negative 0").
• Everything else is true.

This boolean context is relevant for OP_IF, OP_NOTIF, OP_VERIFY, and OP_IFDUP, as well as for determining final success of Script evaluation. Opcodes like OP_BOOLOR and OP_BOOLAND actually interpret their arguments as integers, though the only practical difference is that integer arguments are limited to 4 bytes (violating this limit makes the entire script invalid).