feat(string): add string:lpad and string:rpad

Author: SuperFola

String.ark

@@ -465,17 +465,42 @@
   (let _end (- (len _str) (len _suffix)))
   (= _end (findAfter _str _suffix _end)) }))
 
+# @brief Return a string left padded by a given character _c to make a string of length _n
+# @param _str string to left pad
+# @param _n width of the final string
+# @param _c char to use for padding
+# =begin
+# (print (string:lpad "42" 4 "a"))  # aa42
+# =end
+# @author https://github.com/SuperFola
+(let lpad (fun (_str _n _c) {
+  (assert (= 1 (len _c)) "string:lpad expected a single character to pad")
+  (if (>= (len _str) _n)
+    _str
+    (+ (repeat _c (- _n (len _str))) _str)) }))
+
+# @brief Return a string right padded by a given character _c to make a string of length _n
+# @param _str string to left pad
+# @param _n width of the final string
+# @param _c char to use for padding
+# =begin
+# (print (string:rpad "42" 4 "a"))  # 42aa
+# =end
+# @author https://github.com/SuperFola
+(let rpad (fun (_str _n _c) {
+  (assert (= 1 (len _c)) "string:rpad expected a single character to pad")
+  (if (>= (len _str) _n)
+    _str
+    (+ _str (repeat _c (- _n (len _str))))) }))
+
 # @brief Return a string filled with '0' digits to make a string of length _n
 # @param _str string to left fill
 # @param _n width of the final string
 # =begin
 # (print (string:zfill "42" 4))  # 0042
 # =end
 # @author https://github.com/SuperFola
-(let zfill (fun (_str _n)
-  (if (>= (len _str) _n)
-    _str
-    (+ (repeat "0" (- _n (len _str))) _str))))
+(let zfill (fun (_str _n) (lpad _str _n "0")))
 
 # @brief Return a centered string of length _len, using spaces as fill chars
 # @param _str string to center

tests/string-tests.ark

@@ -125,17 +125,17 @@
       (string:stripMargin "   |hello
                               |abc")
       "hello\nabc")
-  (test:eq
-    (string:stripMargin "hello
-                        |abc
-                        |d")
-    "hello\nabc\nd")
-  (test:eq
-    (string:stripMargin "hello
-                        |
-                        |abc
-                        |d")
-    "hello\n\nabc\nd") })
+    (test:eq
+      (string:stripMargin "hello
+                          |abc
+                          |d")
+      "hello\nabc\nd")
+    (test:eq
+      (string:stripMargin "hello
+                          |
+                          |abc
+                          |d")
+      "hello\n\nabc\nd") })
 
   (test:case "startsWith?" {
     (test:expect (string:startsWith? "hello world" "hello"))
@@ -145,11 +145,27 @@
     (test:expect (string:startsWith? "" "")) })
 
   (test:case "endsWith?" {
-      (test:expect (string:endsWith? "hello world" "world"))
-      (test:expect (not (string:endsWith? "hello world" "World")))
-      (test:expect (not (string:endsWith? "hello world" "hello")))
-      (test:expect (not (string:endsWith? "hello world" "worl")))
-      (test:expect (string:endsWith? "" "")) })
+    (test:expect (string:endsWith? "hello world" "world"))
+    (test:expect (not (string:endsWith? "hello world" "World")))
+    (test:expect (not (string:endsWith? "hello world" "hello")))
+    (test:expect (not (string:endsWith? "hello world" "worl")))
+    (test:expect (string:endsWith? "" "")) })
+
+  (test:case "lpad" {
+    (test:eq (string:lpad "" 4 "1") "1111")
+    (test:eq (string:lpad "2" 4 "1") "1112")
+    (test:eq (string:lpad "22" 4 "1") "1122")
+    (test:eq (string:lpad "222" 4 "1") "1222")
+    (test:eq (string:lpad "2222" 4 "1") "2222")
+    (test:eq (string:lpad "22222" 4 "1") "22222") })
+
+  (test:case "rpad" {
+    (test:eq (string:rpad "" 4 "1") "1111")
+    (test:eq (string:rpad "2" 4 "1") "2111")
+    (test:eq (string:rpad "22" 4 "1") "2211")
+    (test:eq (string:rpad "222" 4 "1") "2221")
+    (test:eq (string:rpad "2222" 4 "1") "2222")
+    (test:eq (string:rpad "22222" 4 "1") "22222") })
 
   (test:case "zfill" {
     (test:eq (string:zfill "" 4) "0000")