These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.98 s (backtrack: 0/20).

[ebuild  N     ] sci-libs/matio-1.5.28:0/13::gentoo  USE="-doc -examples -hdf5 -sparse" 9891 KiB

Total: 1 package (1 new), Size of downloads: 9891 KiB