[m-users.] Higher order term vw. lamda abstraction

[Volker Wysk]

Hi!

The following fails to compile:

    map(string.from_char_list, [['a','b']], L).

Whereas this does compile:

    map( (pred(L1::in, L2::out) is det :- 
	    string.from_char_list(L1, L2)),
         [['a','b']], L).

The error message is:

test_listen.m:013: In clause for `main(di, uo)':
test_listen.m:013:   mode error in conjunction. The next 2 error
messages
test_listen.m:013:   indicate possible causes of this error.
test_listen.m:013:   In clause for `main(di, uo)':
test_listen.m:013:   in call to predicate `list.map'/3:
test_listen.m:013:   mode error: arguments `V_9, V_10, _L' have the
following
test_listen.m:013:   insts:
test_listen.m:013:     free,
test_listen.m:013:     unique,
test_listen.m:013:     free
test_listen.m:013:   which does not match any of the modes for
predicate
test_listen.m:013:   `list.map'/3.
test_listen.m:013:   In clause for `main(di, uo)':
test_listen.m:013:   in argument 1 of call to predicate `map'/3:
test_listen.m:013:   mode error in unification of `V_9' and higher-
order term
test_listen.m:013:   based on multi-moded predicate
`string.from_char_list'/2.
test_listen.m:013:   The modes of the argument variables match more
than one of
test_listen.m:013:   the called predicate's modes.

I don't understand the difference. Shouldn't the two be the same?

Regards,
Volker