Opcodes · arithmetic · enabled

OP_1SUB (0x8c)

Subtracts 1 from the top number. Since May 2025 numbers may be up to 10,000 bytes long (BigInt).

Verified
Stack in → out
a → a-1
Since
Original Bitcoin script
Cost
Base instruction cost 100, plus the result length, plus the result length again to cover number encoding (2025 VM limits).
Bitcoin status
Same in Bitcoin (BTC)BTC limits arithmetic inputs to 4 bytes.

Example

OP_3 OP_1SUB OP_2 OP_EQUAL

Step through it opcode by opcode in Bitauth IDE, the in-browser BCH VM debugger.

Sources

  1. Libauth BCH_2023_05 opcodes (bch-2023-opcodes.ts)
  2. CHIP-2021-05 VM Limits: Targeted Virtual Machine Limits
  3. CHIP-2024-07 BigInt: High-Precision Arithmetic