Aleksej Saushev <[email protected]> writes:
| Aleksej Saushev <[email protected]> writes:
|
| > I seek for enlightement.
|
| Even with all your corrections it still doesn't work,
| both this:
|
| )abbrev package BUG Bug
| Bug(D: Type): Exports == Implementation where
| Exports == with
| dummy: D -> D
| Implementation == add
| iterte: (D -> D, D, NonNegativeInteger) -> D
| iterte(f, p, n) ==
| n = 0 => p
| f(iterte(f, p, subtractIfCan(n, 1)))
^^^^^^^^^^^^^^^^^^^
subtractIfCan does not return a NonNegativeInteger. Rather, its
return type is Union(NonNegativeInteger, "failed").
(In general, the xxxIfCan functions return a Union(D, "failed") where
D is some domain.)
Consequently, you need an explicit coercion to retrieve the
NonNegativeInteger value. The following code compiles with OpenAxiom
)abbrev package BUG Bug
Bug(D: Type): Exports == Implementation where
Exports == with
dummy: D -> D
Implementation == add
iterte: (D -> D, D, NonNegativeInteger) -> D
iterte(f, p, n) ==
n = 0 => p
f(iterte(f, p, subtractIfCan(n, 1)::NonNegativeInteger))
[...]
Personally, I would write the body of 'iterte' without too much fuss
with NonNegativeInteger, as
iterte(f, p, n) ==
n': Integer := n
n = 0 => p
f(iterte(f, p, (n' - 1)::NonNegativeInteger))
The corresponding code uses less CONS and less indirection
(DEFUN |BUG;iterte| (|f| |p| |n| $)
(PROG (#1=#:G780 |n'|)
(RETURN
(SEQ (LETT |n'| |n| |BUGG;iterte|)
(EXIT
(COND ((EQL |n| 0) |p|)
('T
(SPADCALL
(|BUGG;iterte| |f| |p|
(PROG1 (LETT #1# (- |n'| 1) |BUGG;iterte|)
(|check-subtype| (>= #1# 0) '(|NonNegativeInteger|) #1#))
$)
|f|))))))))
| Is there any comprehensible documentation on the syntax and semantics of
| the language?
the AXIOM book is the only written guide/reference to the language
currently available. The rest is some form of collective folklore...
-- Gaby
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