Emacs Lisp: Convert Int/Float, Number/String

Convert Integer to Float

;; int to float
(float 3) ; 3.0

Convert Float to Integer

(truncate 3.3) ; 3

(floor 3.3) ; 3

(ceiling 3.3) ; 4

(round 3.4) ; 3

Numeric Conversions (ELISP Manual)

Convert String and Number

(string-to-number "3")

(number-to-string 3)

(format "%d" 3)
 ;; same as number-to-string but can also do format

[see Emacs Lisp: Format String]

String Conversion (ELISP Manual)