bch-op-codes.md

Intro

May 15th is bringing a network upgrade (also known as a hard fork) to the $BCH network. Along w/ a 32 MB block size we're reactivating a bunch of OP codes. Thanks to the advice of @MADinMelbourne I decided to see exactly what each new OP code was bringing to the table.

Below I list each new OP code w/ a quick description and then demonstrate how it works by showing a small validation script and then what the stack would look like after.

Please let me know if you spot errors. Thanks!

OP_CAT

Concatenates 2 strings

Validation script

'foo' 'bar' OP_CAT

Stack

• 'foobar'

OP_AND

Boolean AND between each bit in the inputs.

Validation script

true false OP_AND

Stack

• false

OP_OR

Boolean OR between each bit in the inputs.

Validation script

true false OP_OR

Stack

• true

OP_XOR

Boolean XOR between each bit in the inputs.

Validation script

true true OP_XOR

Stack

• false

OP_DIV

a is divided by b.

Validation script

10 5 OP_DIV

Stack

• 2

OP_MOD

Returns the remainder after dividing a by b.

Validation script

11 5 OP_MOD

Stack

• 1

OP_SPLIT

Split string at positions

Validation script

'foobar' 2 OP_SPLIT

Stack

• 'obar'
• 'fo'

OP_NUM2BIN

Convert the numeric value into a binary array of a certain size, taking account of the sign bit.

Validation script

12 size OP_NUM2BIN

Stack

• binaryArray

OP_BIN2NUM

Convert the binary array into a valid numeric value, including minimal encoding.

Validation script

binaryArray OP_BIN2NUM

Stack

• 12

OP_RETURN

increasing from 80 bytes to 220 bytes

'foobar' 2 OP_SPLIT would be 'fo' 'obar'. Each char has one byte.

And stack size stays constant because 'foobar' and 2 are stack elements, they become 'fo' and 'obar'

Thanks for the comment. Updating now.

OP_SUBSTR is not being re-enabled. The functionality is provided by OP_SPLIT.

I must misunderstand what I'm reading from https://www.bitcoinabc.org/may15hardfork because it looks like OP_SUBSTR is being enabled. Am I incorrect?

There are also several Bitcoin script operation codes (op codes) being added or reactivated. These include OP_CAT, OP_AND, OP_OR, OP_XOR, OP_DIV, OP_MOD, OP_SPLIT, OP_SUBSTR, OP_NUM2BIN, and OP_BIN2NUM. Finally, the OP_RETURN data carrier size increases to 220 bytes.

I'm getting multiple people (including Deadalnix) telling me that OP_SUBSTR isn't being enabled. I'm removing it from this doc.