Now building a list of strings and joining at the very end rather than concatenating larger and larger strings. More efficient and faster.

Author: Jason Duncan

format-table.el

@@ -172,7 +172,7 @@ Arguments are the list of values ROW, the list of MAX-COL-WIDTHS, and delimiter
 information in OUTPUT-MODE.  Optionally use PAD-FN to pad each column value,
 otherwise values will be padded to the right with spaces."
   (let ((pad-fn (or pad-fn #'format-table-pad-right)))
-    (concat
+    (list
      (plist-get output-mode :begin-row)
      (string-join
       (-zip-with pad-fn row max-col-widths)
@@ -186,12 +186,13 @@ otherwise values will be padded to the right with spaces."
 
 (defun format-table-render-separator-row (max-col-widths output-mode)
   "Given the list of MAX-COL-WIDTHS and delimiter information in OUTPUT-MODE, render a row which separates the header row from the rest of the rows."
-  (concat (plist-get output-mode :separator-begin-row)
-          (string-join
-           (-map #'format-table-generate-dash-string max-col-widths)
-           (plist-get output-mode :separator-col-separator))
-          (plist-get output-mode :separator-end-row)
-          hard-newline))
+  (list
+   (plist-get output-mode :separator-begin-row)
+   (string-join
+    (-map #'format-table-generate-dash-string max-col-widths)
+    (plist-get output-mode :separator-col-separator))
+   (plist-get output-mode :separator-end-row)
+   hard-newline))
 
 (defun format-table-render-json (table)
   "Render the TABLE of values as a json string."
@@ -204,17 +205,16 @@ otherwise values will be padded to the right with spaces."
 (defun format-table-render-table (table output-mode)
   "Given the TABLE of values and delimiter information in OUTPUT-MODE, re-render the table as a string."
   (if (equal output-mode 'json)
-      (format-table-render-json table)
+      (list (format-table-render-json table))
     (let ((top-border-fn (plist-get output-mode :top-border-fn))
           (bottom-border-fn (plist-get output-mode :bottom-border-fn))
           (header-pad-fn (plist-get output-mode :header-pad-fn))
           (max-col-widths (plist-get table :max-col-widths)))
-      (concat
+      (append
        (if top-border-fn (funcall top-border-fn max-col-widths output-mode))
        (format-table-render-row (plist-get table :header) max-col-widths output-mode header-pad-fn)
        (format-table-render-separator-row max-col-widths output-mode)
-       (string-join
-        (--map (format-table-render-row it max-col-widths output-mode) (plist-get table :body)))
+       (apply #'append (--map (format-table-render-row it max-col-widths output-mode) (plist-get table :body)))
        (if bottom-border-fn (funcall bottom-border-fn max-col-widths output-mode))))))
 
 (defun format-table-render-row-count (count output-mode)
@@ -266,9 +266,11 @@ otherwise values will be padded to the right with spaces."
          (table (format-table-cleanup-and-parse str input-mode)))
     (if (not table)
         str
-      (concat
-       (format-table-render-table table output-mode)
-       (format-table-render-row-count (plist-get table :row-count) output-mode)))))
+      (string-join
+       (append
+        (format-table-render-table table output-mode)
+        (list
+         (format-table-render-row-count (plist-get table :row-count) output-mode)))))))
 
 (provide 'format-table)
 ;;; format-table.el ends here

test/format-table-test.el

@@ -1,6 +1,7 @@
 ;; -*- lexical-binding: t -*-
 
 (require 'ert)
+(require 'format-table)
 (require 'format-table-test-helper)
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -105,39 +106,52 @@
 (ert-deftest format-table-render-row-should-render-row-for-ms ()
   (let ((expected "foo bar
 ")
-        (actual (format-table-render-row '("foo" "bar") '(3 3) (alist-get 'ms format-table-format-alist))))
+        (actual
+         (string-join
+          (format-table-render-row
+           '("foo" "bar") '(3 3) (alist-get 'ms format-table-format-alist)))))
     (should (string-equal expected actual))))
 
 (ert-deftest format-table-render-row-should-render-row-for-org ()
   (let ((expected "| foo | bar |
 ")
-        (actual (format-table-render-row '("foo" "bar") '(3 3) (alist-get 'org format-table-format-alist))))
+        (actual
+         (string-join
+          (format-table-render-row '("foo" "bar") '(3 3) (alist-get 'org format-table-format-alist)))))
     (should (string-equal expected actual))))
 
 (ert-deftest format-table-render-row-should-render-row-for-mysql ()
   (let ((expected "| foo | bar |
 ")
-        (actual (format-table-render-row '("foo" "bar") '(3 3) (alist-get 'mysql format-table-format-alist))))
+        (actual
+         (string-join
+          (format-table-render-row '("foo" "bar") '(3 3) (alist-get 'mysql format-table-format-alist)))))
     (should (string-equal expected actual))))
 
 ;;;;;;;;format-table-render-separator-row;;;;;;;;;
 
 (ert-deftest format-table-render-separator-row-should-render-separator-row-for-ms ()
   (let ((expected "--- ---
 ")
-        (actual (format-table-render-separator-row '(3 3) (alist-get 'ms format-table-format-alist))))
+        (actual
+         (string-join
+          (format-table-render-separator-row '(3 3) (alist-get 'ms format-table-format-alist)))))
     (should (string-equal expected actual))))
 
 (ert-deftest format-table-render-separator-row-should-render-separator-row-for-org ()
   (let ((expected "|-----+-----|
 ")
-        (actual (format-table-render-separator-row '(3 3) (alist-get 'org format-table-format-alist))))
+        (actual
+         (string-join
+          (format-table-render-separator-row '(3 3) (alist-get 'org format-table-format-alist)))))
     (should (string-equal expected actual))))
 
 (ert-deftest format-table-render-separator-row-should-render-separator-row-for-mysql ()
   (let ((expected "+-----+-----+
 ")
-        (actual (format-table-render-separator-row '(3 3) (alist-get 'mysql format-table-format-alist))))
+        (actual
+         (string-join
+          (format-table-render-separator-row '(3 3) (alist-get 'mysql format-table-format-alist)))))
     (should (string-equal expected actual))))
 
 ;;;;;;;;;;;;;;format-table-split-row;;;;;;;;;;;;;;