t_root seqlit act orseq_form andseq_form orseq_form I andseq_form I seqlit act I fails( act ) act constant I act_var orseq( (andseq_form I secrliti(2,) ) andseq( (orseq_form I secrliti(2,) ) 21.7 Program Transformations A program transformation is any type-preserving mapping from expressions t