.TH Project
.PP
Keeps only a subset of attributes.
.SH Signature
.PP
.RS
.nf
project(operand: Relation, attributes: AttrList) -> Relation
.fi
.RE
.SH Examples
.PP
.RS
.nf
project(suppliers, [:city])
.fi
.RE
.PP
.RS
.nf
project(suppliers, [:city], allbut: true)
.fi
.RE
.SH Description
.PP
Computes the relation obtained by projecting tuples from \fB\fCoperand\fR on a
subset of their attributes.
.PP
This operator supports an ALL BUT variant, through the \fB\fCallbut\fR option.
When set to true, the operator \fIremoves\fP specified attributes instead of
keeping them. An \fB\fCallbut\fR operator is also provided that has the same
effect.
.SH Implementation notes
.PP
Unlike SQL, this operator ALWAYS remove duplicates. There is no way, in
Alf, to compute \fIbags\fP of tuples.