Sequences

The function (RefLink[Flatten, paclet:ref/Flatten]) allows you to explicitly flatten out all sublists:

Flatten[{a,{b,c},{d,e}}]

(RefLink[FlattenAt, paclet:ref/FlattenAt]) lets you specify at what positions you want sublists flattened:

FlattenAt[{a,{b,c},{d,e}},2]

(RefLink[Sequence, paclet:ref/Sequence]) objects automatically get spliced in, and do not require any explicit flattening:

{a,Sequence[b,c],Sequence[d,e]}

Representing sequences of arguments in functions.

(RefLink[Sequence, paclet:ref/Sequence]) works in any function:

f[Sequence[a,b],c]

This includes functions with special input forms:

a==Sequence[b,c]

Here is a common way that (RefLink[Sequence, paclet:ref/Sequence]) is used:

{a,b,f[x,y],g[w],f[z,y]}/.f->Sequence