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21.2.2 Integers

Integers are whole numbers, that is numbers with no fractional part, such as 2, 83 and -3789.

Integers in Guile can be arbitrarily big, as shown by the following example.

(define (factorial n)
  (let loop ((n n) (product 1))
    (if (= n 0)
        (loop (- n 1) (* product n)))))

(factorial 3)

(factorial 20)

(- (factorial 45))

Readers whose background is in programming languages where integers are limited by the need to fit into just 4 or 8 bytes of memory may find this surprising, or suspect that Guile's representation of integers is inefficient. In fact, Guile achieves a near optimal balance of convenience and efficiency by using the host computer's native representation of integers where possible, and a more general representation where the required number does not fit in the native form. Conversion between these two representations is automatic and completely invisible to the Scheme level programmer.

integer? x Scheme Procedure
scm_integer_p (x) C Function
Return #t if x is an integer number, else #f.
(integer? 487)

(integer? -3.4)