• ← BlankNullSequence

BlankSequence

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BlankSequence[]

__

represents any non-empty sequence of expression elements in a pattern.

BlankSequence[h]

__h

represents any sequence of elements, all of which have head h.

Use a BlankSequence pattern to stand for a non-empty sequence of arguments:

• • MatchQ[f[1, 2, 3], f[__]]

• • MatchQ[f[], f[__]]

__h will match only if all elements have head h:

• • MatchQ[f[1, 2, 3], f[__Integer]]

• • MatchQ[f[1, 2.0, 3], f[__Integer]]

The value captured by a named BlankSequence pattern is a Sequence object:

• • f[1, 2, 3] /. f[x__] -> x