Definition of `Idx`

Question

idx is an integer in source code of bitcoin related softwares.

https://github.com/decred/atomicswap/blob/70f795e/cmd/btcatomicswap/main.go#L391

https://github.com/btcsuite/btcd/blob/efa50e6abc7a9be4478e44216a0677efa8fdf4ce/txscript/stack.go#L108

https://github.com/bitcoin/bitcoin/blob/aa624b61c928295c27ffbb4d27be582f5aa31b56/src/qt/bitcoinaddressvalidator.cpp#L32

What does idx stand for?

Answer 1

idx = index, as in the index of an array/list or similar data structure, usually (and in most cases such as this one) an index is zero-based, meaning the first element of the array has an index of 0, the second has an index of 1, and so on.