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+

+ Function

Syntax:

+ &rest numbers → sum

Arguments and Values:

number—a number .

sum—a number .

Description:

Returns the sum of numbers, performing any necessary type conversions in the process. If no numbers are supplied, 0 is returned.

Examples:


(+) → 0 
(+ 1) → 1 
(+ 31/100 69/100) → 1 
(+ 1/5 0.8) → 1.0

Exceptional Situations:

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

See Also:

Section 12.1.1 (Numeric Operations), Section 12.1.3 (Rational Computations), Section 12.1.4 (Floating-point Computations), Section 12.1.5 (Complex Computations)

Expanded Reference: +​

Basic addition​

+ returns the sum of its arguments. With no arguments, it returns the additive identity 0.

(+)
=> 0
(+ 5)
=> 5
(+ 2 3)
=> 5
(+ 1 2 3 4 5)
=> 15

Rational arithmetic​

When all arguments are rationals (integers or ratios), the result is exact.

(+ 1/3 1/3 1/3)
=> 1
(+ 31/100 69/100)
=> 1
(+ 1/6 1/3)
=> 1/2

Floating-point contagion​

If any argument is a float, the result is a float due to floating-point contagion rules.

(+ 1 2.0)
=> 3.0
(+ 1/5 0.8)
=> 1.0
(+ 1 2.0d0)
=> 3.0d0

Complex number addition​

+ works with complex numbers, performing component-wise addition.

(+ #c(1 2) #c(3 4))
=> #C(4 6)
(+ #c(3 -5) 7)
=> #C(10 -5)
(+ #c(1.0 2.0) #c(0.0 -2.0))
=> #C(1.0 0.0)

Accumulating a sum with reduce​

+ is commonly used with reduce to sum the elements of a sequence.

(reduce #'+ '(10 20 30 40))
=> 100
(reduce #'+ '() :initial-value 0)
=> 0