[seqfan] Concatenation: summary

[Charles Greathouse]

As I understood it, the consensus was that anything could be used to
represent concatenation, as long as the use is explained.  Here are
the formats I've found -- not an exhaustive list, but should cover the
most popular:

a1 // a2 is used in A115429 (as in Fortran).
a1 . a2 is used in A115437 (as in Perl).
a1 : a2 is used in A089591.
a1 ^ a2 is used in A091975 (c.f. A091844).
a1_a2 is used in A153164.
a1a2 is used in A089710.
a1 U a2 is used in A165784.
'a1 followed by a2' is used in A034821.
a1 & a2 and a1 + a2 may also be used.

Pari uses eval(Str(a1, a2, ..., an)).
Maple uses parse(cat(a1, a2, ..., an)).
Mathematica uses FromDigits[Join[IntegerDigits[a1], IntegerDigits[a2],
..., IntegerDigits[an]]] or ToExpression[StringJoin[ToString[a1],
ToString[a2], ..., ToString[an]]] or
FromDigits["a1"<>"a2"<>...<>"an"].

Charles Greathouse
Analyst/Programmer
Case Western Reserve University