A. Common Exceptions

Common Exceptions

undef_type

! undef_type(xxx)

This is a sign that the type xxx is not defined in your grammar. Check the spelling of your type feature structure.

unsatisfiable lexical entry

{ALE: ERROR: lex: unsatisfiable lexical entry for i

This is an error caused by a lexical entry that is impossible to satisfy. For example, the following definition of i will yield this error as subjective cannot be a type of sem.

i ---> (np, sem:subjective, agr:(person:first, case:subjective)).

Appending to an uninitialized list (TRALE will hang)

bot sub [cat, list].
    cat sub [a,b,c] intro [list:list].
    list sub [e_list, ne_list].
        ne_list intro [hd:bot, tl:list].

a ---> a.
b ---> b.

append([],Xs,Xs) if true.
append([H|T1],L2,[H|T2]) if append(T1,L2,T2).

this_will_hang rule
    (c, list:Result) ===>
    cat> (a, list:List),
    cat> (b, B),
    goal> append(List, [B], Result).

Appending to an uninitialized list will cause an infinite loop.

| ?- rec[a,b].

STRING: 
0 a 1 b 2
^CProlog interruption (h for help)? a

You can interrupt the program by ctrl + c, then enter a to abort.

To solve the problem, you need to initialize the list somewhere, either in the lexical entry:

a ---> (a, list:[]).

or in the rules.

    cat> (a, list:(List, [])),

! ale(feat_intro(...))

a sub [b, c, f].
    b intro [f:f].
    c intro [f:f].

TRALE does not allow duplicated feature names for types that do not inherent each other.

To solve this problem, either rename the features, or group the types into a supertype.

a sub [b_c, f].
    b_c sub [b, c] intro [f: f].