>>>>> "Christoph" == Christoph Breitkopf <[EMAIL PROTECTED]> writes:
Christoph> Hello,
Christoph> I have a problem that the return type from aref does
Christoph> not agree with the declared element type of the array.
Christoph> Here is a short test program:
Christoph> (declaim (optimize (speed 2) (safety 2)
Christoph> (extensions:inhibit-warnings 0)))
Christoph> (defun elem-length (x i)
Christoph> (declare (type (simple-array simple-base-string 1) x))
Christoph> (let ((s (aref x i)))
Christoph> ; (declare (type simple-base-string s))
Christoph> (length s)))
[snip]
Christoph> ; In: DEFUN ELEM-LENGTH
Christoph> ; (LENGTH S)
Christoph> ; Note: Unable to optimize due to type uncertainty:
Christoph> ; The first argument is a (OR NULL VECTOR CONS), not a
(SIMPLE-ARRAY * (*)).
Christoph> ;
Christoph> ; Note: Unable to optimize due to type uncertainty:
Christoph> ; The first argument is a (OR NULL VECTOR CONS), not a VECTOR.
Christoph> ;
Christoph> ; Note: Forced to do static-function Length (cost 52).
Christoph> ; Unable to do LENGTH/LIST (cost 40) because:
Christoph> ; The first argument is a (OR NULL VECTOR CONS), not a LIST.
Christoph> ...
Christoph> Why does the compiler infer (OR NULL VECTOR CONS) for (aref x i)?
I think this happens because CMUCL doesn't have a specialized array
type for arrays with simple-base-string. Thus, the actual type of the
array is (simple-array T 1). Compare with what
upgraded-array-element-type says for simple-base-string.
Earlier versions would trust your declared element-type, but later
versions took this out as being unsafe because the compiler and
runtime couldn't really prove it was true. For example, you could
call elem-length with any 1D simple-array and bad things could happen
if it wasn't really a (simple-array simple-base-string 1).
Ray
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