陣列升級

Question

如果我正確理解Common Lisp標準的Section 15.1.2.1，則(upgraded-array-element-type '(unsigned-byte 8))爲'(unsigned-byte 16)或甚至t是完全合法的。因此我的問題是關於實現的實際行爲。

當前是否有任何實現在使用'(unsigned-byte 8)或'(unsigned-byte 16)進行升級？換句話說，當下面的是假：

(and (subtypep (upgraded-array-element-type '(unsigned-byte 8)) '(unsigned-byte 8)) 
    (subtypep (upgraded-array-element-type '(unsigned-byte 16)) '(unsigned-byte 16)) 

（表達爲SBCL，CLISP，快板CL，CL Clozure和LispWorks真。）

Answer 1

ECL可能不支持'(unsigned-byte 16)