How to Control Padding Programmatically in Clojure and Common Lisp Format

How can I programmatically control padding in Clojure (java.util.Formatter) and Common Lisp (cl-format)?

Both Clojure and Common Lisp offer formatting functionalities that allow controlled output through padding. However, their approaches differ: Clojure uses the `java.util.Formatter` while Common Lisp utilizes `cl-format`. In this detailed explanation, we will explore how to properly apply padding in both languages to achieve the desired formatted output.

;; Clojure Example
(defn format-with-padding [text]
  (let [formatted (String/format "%6s" text)]
    formatted))
;; Usage
(format-with-padding "test") ;; returns "  test"

;; Common Lisp Example
(cl:cl-format t "~6A~%" "test") ;; outputs "  test".

Causes

• Misunderstanding the formatting syntax in Clojure's `java.util.Formatter`.
• Lack of familiarity with Common Lisp's `cl-format` directives.

Solutions

• For Clojure, use formatting flags in java.util.Formatter, such as `%6s` to specify minimum width and padding. Example: `String.format("%6s", "test")` computes to " test".
• In Common Lisp, utilize `cl-format` with directives like `~{~A~^,~}` to control padding and alignment. Example: `(cl:cl-format nil "~6A" "test")` results in " test".

Mistake: Using incorrect formatting specifiers leading to unexpected outputs in Clojure.

Solution: Ensure that the correct flags are applied in the formatter. Refer to the java.util.Formatter documentation to confirm usage.

Mistake: Not accounting for dynamic string lengths in Common Lisp leading to misaligned outputs.

Solution: Always validate and dynamically adjust the field width in `cl-format` based on input length.