experiment: rascal formatter based on Box and layoutDiff

pom.xml

@@ -173,7 +173,7 @@
                         </goals>
                         <configuration>
                             <isPackageCourse>false</isPackageCourse>
-                            <errorsAsWarnings>false</errorsAsWarnings>
+                            <errorsAsWarnings>true</errorsAsWarnings>
                             <bin>${project.build.outputDirectory}</bin>
                             <funding>${project.basedir}/FUNDING</funding>
                             <citation>${project.basedir}/CITATION.md</citation>

src/org/rascalmpl/library/IO.rsc

@@ -140,8 +140,9 @@ Append a textual representation of some values to an existing or a newly created
 *  All other values are printed as-is.
 *  Each value is terminated by a newline character.
 
-The existing file can be stored using any character set possible, if you know the character set, please use ((appendToFileEnc)).
-Else the same method of deciding the character set is used as in ((readFile)).
+The existing file can be stored using any character set possible. 
+If you know the character set, please use the `charset` keyword parameter.
+Otherwise, the same method of deciding the character set is used as in ((readFile)).
 }
 @pitfalls{
 *  The same encoding pitfalls as the ((readFile)) function.

src/org/rascalmpl/library/List.rsc

@@ -19,7 +19,7 @@ module List
 
 import Exception;
 import Map;
-
+import String;
 
 @synopsis{Concatenate a list of lists.}
 @examples{
@@ -259,8 +259,7 @@ intercalate(", ", ["zebra", "elephant", "snake", "owl"]);
 ```
 }
 str intercalate(str sep, list[value] l) = 
-  "<for(int i <- index(l)){><i == 0 ? "" : sep><l[i]><}>";
-
+  "<for (value e <- l) {><e><sep><}>"[..-size(sep)];
 
 @synopsis{Intersperses a list of values with a separator.}
 @examples{
@@ -272,9 +271,8 @@ intersperse(1, []);
 intersperse([], [1]);
 ```
 }
-list[&T] intersperse(&T sep, list[&T] xs) = 
-  (isEmpty(xs))? [] : ([head(xs)] | it + [sep,x] | x <- tail(xs));
-
+list[&T] intersperse(&T sep, list[&T] xs) =
+  [x, sep | &T x <- xs][..-1];
 
 @synopsis{Test whether a list is empty.}
 @description{
@@ -655,6 +653,29 @@ tuple[list[&T],list[&T]] split(list[&T] l) {
 	return <take(half,l), drop(half,l)>;
 }
 
+@synopsis{Groups sublists for consecutive elements which are `similar`}
+@description{
+This function does not change the order of the elements. Only elements
+which are similar end-up in a sub-list with more than one element. The
+elements which are not similar to their siblings, end up in singleton
+lists.
+}
+@examples{
+```rascal-shell
+import List;
+bool bothEvenOrBothOdd(int a, int b) = (a % 2 == 0 && b % 2 == 0) || (a % 2 == 1 && b % 2 == 1);
+group([1,7,3,6,2,9], bothEvenOrBothOdd);
+```
+}
+public list[list[&T]] group(list[&T] input, bool (&T a, &T b) similar) {
+  lres = while ([hd, *tl] := input) {
+      sim = [hd, *takeWhile(tl, bool (&T a) { return similar(a, hd); })];
+	    append sim;
+	    input = drop(size(sim), input);
+  }
+
+  return lres; 
+}
 
 @synopsis{Sum the elements of a list.}
 @examples{