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judymcconville@roadrunner.com 2017-05-01 12:34:12 -07:00
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@ -427,7 +427,7 @@ When reading Bitcoin Script, remember that the condition being evaluated comes _
==== Conditional Clauses with VERIFY Opcodes ==== Conditional Clauses with VERIFY Opcodes
((("VERIFY opcodes")))((("IF clauses")))Another form of conditional in Bitcoin Script is any opcode that ends in +VERIFY+. The +VERIFY+ suffix means that if the condition evaluated is not +TRUE+, execution of the script terminates immediately and the transaction is deemed invalid. ((("VERIFY opcodes")))((("IF clauses")))((("opcodes", "VERIFY")))Another form of conditional in Bitcoin Script is any opcode that ends in +VERIFY+. The +VERIFY+ suffix means that if the condition evaluated is not +TRUE+, execution of the script terminates immediately and the transaction is deemed invalid.
((("guard clauses")))Unlike an +IF+ clause, which offers alternative execution paths, the +VERIFY+ suffix acts as a _guard clause_, continuing only if a precondition is met. ((("guard clauses")))Unlike an +IF+ clause, which offers alternative execution paths, the +VERIFY+ suffix acts as a _guard clause_, continuing only if a precondition is met.
@ -470,7 +470,7 @@ So, when do we use +VERIFY+ and when do we use +IF+? If all we are trying to do
[TIP] [TIP]
==== ====
An opcode such as +EQUAL+ will push the result (+TRUE+/+FALSE+) onto the stack, leaving it there for evaluation by subsequent opcodes. In contrast, the opcode +EQUALVERIFY+ suffix does not leave anything on the stack. Opcodes that end in +VERIFY+ do not leave the result on the stack. ((("EQUAL opcodes")))((("opcodes", "EQUAL")))((("EQUALVERIFY opcode")))((("opcodes", "EQUALVERIFY")))An opcode such as +EQUAL+ will push the result (+TRUE+/+FALSE+) onto the stack, leaving it there for evaluation by subsequent opcodes. In contrast, the opcode +EQUALVERIFY+ suffix does not leave anything on the stack. Opcodes that end in +VERIFY+ do not leave the result on the stack.
==== ====
==== Using Flow Control in Scripts ==== Using Flow Control in Scripts