quick study

'I mustn't be cracking jokes though, for I've got a part of twelve lengths here, which I must be up in tomorrow night, and I haven't had time to look at it yet; I'm a confounded quick study, that's one comfort.'

Gilpatric assumed that his own prior experience would give him an early advantage over McNamara, but this proved erroneous, as McNamara was a quick study and soon got a fix on the management and organization of the Defense Department.