.TH Sum
.PP
Arithmetic sum
.SH Signature
.PP
.RS
.nf
sum(expr: AttrName|(Tuple->Numeric)) -> Aggregator
.fi
.RE
.SH Examples
.PP
.RS
.nf
sum(:qty)
.fi
.RE
.PP
.RS
.nf
sum{|t| t.qty * t.price }
.fi
.RE
.PP
.RS
.nf
sum(->(t){ t.qty * t.price })
.fi
.RE
.SH Description
.PP
Computes \fB\fCv1 + v2 + ... + vn\fR\&.
.SH Implementation notes
.PP
This aggregate function should only be used with numeric types. As of
current Alf version, it does not aggregate empty sets correctly on
non\-numeric data types.