default for <i>READ-DEFAULT-FLOAT-FORMAT</i>  is implementation dependent and can be changed by user.<p>In CL type float has subtypes single-float, double-float, short-float, and long-float.  &quot;Any two of them must be either disjoint types or the same type; if the same type, then any other types between them in the above ordering must also be the same type. For example, if the type single-float and the type long-float are the same type, then the type double-float must be the same type also.&quot;<p>If there is only one float representation it has to be `(typep x &#x27;single-float)` but if the internal representation is different (double-float for example) it can be all of the types. At least this is how I understand the spec.<p><a href="http:&#x2F;&#x2F;clhs.lisp.se&#x2F;Body&#x2F;v_rd_def.htm#STread-default-float-formatST" rel="nofollow">http:&#x2F;&#x2F;clhs.lisp.se&#x2F;Body&#x2F;v_rd_def.htm#STread-default-float-f...</a><p><a href="http:&#x2F;&#x2F;clhs.lisp.se&#x2F;Body&#x2F;t_float.htm#float" rel="nofollow">http:&#x2F;&#x2F;clhs.lisp.se&#x2F;Body&#x2F;t_float.htm#float</a><p><a href="http:&#x2F;&#x2F;clhs.lisp.se&#x2F;Body&#x2F;t_short_.htm" rel="nofollow">http:&#x2F;&#x2F;clhs.lisp.se&#x2F;Body&#x2F;t_short_.htm</a>