Exercises for May 25. Please attempt the following exercises *in addition to* all 1-star exercises. Mail your completed scripts to me (apt@cs.pdx.edu) by the beginning of class on Tuesday 5/25. Remember to work broadly as well as deeply. Don't get stuck on any one problem for too long (especially not the extra problems towards the ends of the chapters). Stlc.v: typing_nonexample_3 typable_empty__closed subject_expansion_stlc progress' unique_types stlc_variation1 stlc_variation2 MoreStlc.v: STLC_extensions: complete all the proofs for these features (only): unit, pairs, sums, numbers, fix.