T,U,V,W: term
X,Y,Z : reserved: transient objet denoted by a capital letter
-a :
+a : applicability condition (true = restricted, false = general)
b : local dropping kind parameter (true = restricted, false = general)
c : rt-reduction count parameter
d : term degree
h : sort hierarchy parameter
i,j : local reference depth (de Bruijn's)
k,l : global reference level
-m :
-n : type iterations
+m,n : iterations
o : sort degree parameter (origin)
p,q : binder polarity
r :
2: binary
A: application to vector
+E: empty list
F: boolean false
T: boolean true
b: generic binder with one argument
d: abbreviation
f: generic flat with one argument
+i: generic binder for local environments
l: typed abstraction
n: native type annotation
u: generic binder with zero argument