Add mnswap macro

basis/generalizations/generalizations-tests.factor

@@ -38,3 +38,7 @@ IN: generalizations.tests
 [ "a" ] [ { "a" } 1 firstn ] unit-test
 
 [ [ 1 2 ] ] [ 1 2 2 [ ] nsequence ] unit-test
+
+[ 4 5 1 2 3 ] [ 1 2 3 4 5 2 3 mnswap ] unit-test
+
+[ 1 2 3 4 5 6 ] [ 1 2 3 4 5 6 2 4 mnswap 4 2 mnswap ] unit-test

basis/generalizations/generalizations.factor

@@ -73,3 +73,6 @@ MACRO: napply ( n -- )
     2 [a,b]
     [ [ 1- ] [ ] bi '[ _ ntuck _ nslip ] ]
     map concat >quotation [ call ] append ;
+
+MACRO: mnswap ( m n -- )
+    1+ '[ _ -nrot ] <repetition> spread>quot ;