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10.4 Special named constants

Constant: #!optional

Special self-evaluating literal used in lambda parameter lists before optional parameters.

Constant: #!rest

Special self-evaluating literal used in lambda parameter lists before the rest parameter.

Constant: #!key

Special self-evaluating literal used in lambda parameter lists before keyword parameters.

Constant: #!eof

The end-of-file object.

Note that if the Scheme reader sees this literal at top-level, it is returned literally. This is indistinguishable from coming to the end of the input file. If you do not want to end reading, but want the actual value of #!eof, you should quote it.

Constant: #!void

The void value. Same as (values). If this is the value of an expression in a read-eval-print loop, nothing is printed.

Constant: #!null

The Java null value. This is not really a Scheme value, but is useful when interfacing to low-level Java code.