Opcode Explained

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OP_BOOLOR ​

INFO

Opcode number: 155
Byte representation: 0x9b
Short description: Pop the top two stack items and push 1 if either is nonzero, else push 0.

OP_BOOLOR performs a logical OR operation on the top two items on the stack. If either item is non-zero, it pushes 1 (true) onto the stack. If both items are zero (or empty arrays), it pushes an empty array (false). Both items are interpreted as integers, and must therefore be 4 bytes long or less. If either is above 4 bytes in length, the script is invalid.

Operation ​

  1. Remove the top two items from the stack:
    • If either item is non-zero, push 1 (true) onto the stack.
    • If both items are zero ([] or a 0-value integer), push an empty array (false).
  2. Replace the top two items with the result.

Notes ​

  • If there are fewer than two items on the stack when OP_BOOLOR is executed, the script will fail.

Examples ​

Example 1: Both items are true ​

shell
# ASM script
OP_1 OP_1 OP_BOOLOR

# Raw script
51919b

# Stack (before OP_BOOLOR)
1  # top
1

# Stack (after OP_BOOLOR)
1  # true, as both items are non-zero

Example 2: One item is true ​

shell
# ASM script
OP_1 OP_0 OP_BOOLOR

# Raw script
51009b

# Stack (before OP_BOOLOR)
0  # top (false)
1

# Stack (after OP_BOOLOR)
1  # true, as one item was non-zero

Example 3: Both items are false ​

shell
# ASM script
OP_0 OP_0 OP_BOOLOR

# Raw script
00909b

# Stack (before OP_BOOLOR)
0  # top
0

# Stack (after OP_BOOLOR)
[]  # false, as both items were zero

Example 4: Non-empty arrays as true ​

shell
# ASM script
OP_PUSHBYTES_2 a4b6 OP_5 OP_BOOLAND

# Raw script
02a4b6559b

# Stack (before OP_BOOLAND)
5
a4b6

# Stack (after OP_BOOLAND)
1