Syntax:

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 

Affected By: None.

Exceptional Situations:

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

See Also:

incf, decf

Notes:

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