1+, 1- (Function)

Syntax:

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:

incf, 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.