Implement global ++/-- functions

src/globals.apfl

@@ -108,6 +108,9 @@
 
     is := -named 'is (partial has identity)
 
+    ++ := { x -> + x 1 }
+    -- := { x -> - x 1 }
+
     -raw-substring := builtins.substring
     substr := {
     start s ->
@@ -136,7 +139,7 @@
             sep-len := len sep
             parts := []
             loop {
-                if (maxlen-reached (+ 1 (len parts))) {
+                if (maxlen-reached (++ (len parts))) {
                     parts = [~parts s]
                     false
                 } {
@@ -239,6 +242,8 @@
         '!< -> !<
         '!>= -> !>=
         '!<= -> !<=
+        '++ -> ++
+        '-- -> --
         'keach -> keach
         'each -> each
         'get-optional -> get-optional