We prove a Givental-style mirror theorem for toric Deligne--Mumford stacks X.
This determines the genus-zero Gromov--Witten invariants of X in terms of an
explicit hypergeometric function, called the I-function, that takes values in
the Chen--Ruan orbifold cohomology of X.Comment: 35 pages. v2: key references added. v3: errors corrected; formal
setup changed; proofs simplified, clarified, and shortened; references added.
v4: references updated. v5: references update
