1+, 1- [Function]

1 + => number {successor} 1 - => number {predecessor}

Arguments and Values::

number---a number.

successor, predecessor---a number.

Description::

1+ returns a number that is one more than its argument number. 1- returns a number that is one less than its argument number.

Examples::

 (1+ 99) =>  100 
 (1- 100) =>  99 
 (1+ (complex 0.0)) =>  #C(1.0 0.0) 
 (1- 5/3) =>  2/3 

Exceptional Situations::

Might signal type-error if its argument is not a number. Might signal arithmetic-error.

See Also::

@xref{incf; decf} , decf

Notes::

 (1+ number) == (+ number 1)
 (1- number) == (- number 1)

Implementors are encouraged to make the performance of both the previous expressions be the same.

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