type_of x ctx returns the type of x in the context ctx when it appears in it, and

• raises [Not_found]

  otherwise.

def_of x ctx returns the definition of x in the context ctx if it appears, and None otherwise

mem x ctx tells whether variable x is mapped in the context ctx.

to_prod ctx t builds a product by abstracting over the context ctx, in the term t. It returns the number of products as well.

to_prod_box bctx t is similar to to_prod bctx t but operates on boxed contexts and terms.

box_context ctx lifts context ctx to a boxed context.

to_abst ctx t builds a sequence of abstractions over the context ctx, in the term t.

to_let ctx t adds the defined variables of ctx on top of t.

sub ctx vs returns the sub-context of ctx made of the variables of vs.

unfold ctx t behaves like Term.unfold unless term t is of the form Vari(x) with x defined in ctx. In this case, t is replaced by the definition of x in ctx. In particular, if no operation is carried out on t, we have unfold ctx t == t.

get_args ctx t decomposes term t as Term.get_args does, but any variable encountered is replaced by its definition in ctx (if it exists).

to_map builds a map from a context.