Unreadable objects

#<type ...>

all STRUCTURE-OBJECTs lacking a keyword constructor

#<ARRAY type dimensions>

all ARRAYs except STRINGs, if *PRINT-ARRAY* is NIL

#<SYSTEM-FUNCTION name>

built-in function written in C

#<ADD-ON-SYSTEM-FUNCTION name>

module function written in C

#<SPECIAL-OPERATOR name>

special operator handler

#<COMPILED-FUNCTION name>

compiled function, if CUSTOM:*PRINT-CLOSURE* is NIL

#<FUNCTION name ...>

interpreted function, , if CUSTOM:*PRINT-CLOSURE* is NIL

#<FRAME-POINTER #x...>

pointer to a stack frame

#<DISABLED POINTER>

frame pointer which has become invalid on exit from the corresponding BLOCK or TAGBODY

#<...STREAM...>

STREAM

#<PACKAGE name>

PACKAGE

#<HASH-TABLE #x...>

HASH-TABLE, if *PRINT-ARRAY* is NIL

#<READTABLE #x...>

READTABLE

#<SYMBOL-MACRO form>

SYMBOL-MACRO handler

#<MACRO function>

macro expander (defined by DEFMACRO and friends)

#<FFI:FOREIGN-POINTER #x...>

foreign pointer (Platform Dependent: UNIX, Win32 platforms only.)

#<FFI:FOREIGN-ADDRESS #x...>

foreign address (Platform Dependent: UNIX, Win32 platforms only.)

#<FFI:FOREIGN-VARIABLE name #x...>

foreign variable (Platform Dependent: UNIX, Win32 platforms only.)

#<FFI:FOREIGN-FUNCTION name #x...>

foreign function (Platform Dependent: UNIX, Win32 platforms only.)

#<UNBOUND>

“value” of an unbound symbol, an unsupplied optional or keyword argument

#<SPECIAL REFERENCE>

environment marker for variables declared SPECIAL

#<DOT>

internal READ result for “.”

#<END OF FILE>

internal READ result, when the end-of-stream is reached

#<READ-LABEL ...>

intermediate READ result for #n#

#<ADDRESS #x...>

machine address, should not occur

#<SYSTEM-POINTER #x...>

should not occur