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Merge pull request #497 from theStack/twofewerops

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script opcode count IF vs. VERIFY: diff is two ops
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Andreas M. Antonopoulos 2018-02-14 14:56:16 -06:00 committed by GitHub
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@ -498,7 +498,7 @@ Bob's unlocking script is identical:
<Bob's Sig> <hash pre-image>
----
The script with +IF+ does the same thing as using an opcode with a +VERIFY+ suffix; they both operate as guard clauses. However, the +VERIFY+ construction is more efficient, using one fewer opcode.
The script with +IF+ does the same thing as using an opcode with a +VERIFY+ suffix; they both operate as guard clauses. However, the +VERIFY+ construction is more efficient, using two fewer opcodes.
So, when do we use +VERIFY+ and when do we use +IF+? If all we are trying to do is to attach a precondition (guard clause), then +VERIFY+ is better. If, however, we want to have more than one execution path (flow control), then we need an +IF...ELSE+ flow control clause.