阵列升级

Question

如果我正确理解Common Lisp标准的Section 15.1.2.1，则(upgraded-array-element-type '(unsigned-byte 8))为'(unsigned-byte 16)或甚至t是完全合法的。因此我的问题是关于实现的实际行为。

当前是否有任何实现在使用'(unsigned-byte 8)或'(unsigned-byte 16)进行升级？换句话说，当下面的是假：

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

（表达为SBCL，CLISP，快板CL，CL Clozure和LispWorks真。）

Answer 1

ECL可能不支持'(unsigned-byte 16)