Adding WIP alternate case approach.

common/altcase.fs

@@ -0,0 +1,54 @@
+\ Copyright 2022 Bradley D. Nelson
+\
+\ Licensed under the Apache License, Version 2.0 (the "License");
+\ you may not use this file except in compliance with the License.
+\ You may obtain a copy of the License at
+\
+\     http://www.apache.org/licenses/LICENSE-2.0
+\
+\ Unless required by applicable law or agreed to in writing, software
+\ distributed under the License is distributed on an "AS IS" BASIS,
+\ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+\ See the License for the specific language governing permissions and
+\ limitations under the License.
+
+( A WIP exploration of an optimized version of CASE. )
+( NOTE: NOT YET FUNCTIONAL )
+( TODO: complete this )
+
+internals definitions
+create case-buffer 400 cells allot
+variable cases
+variable default-target  variable default-fixup
+: case, ( n -- ) case-buffer cases @ cells + ! 1 cases +! ;
+forth definitions internals
+
+( default num target fixup )
+
+: CASE ( n -- )
+  0 cases !  0 default-target !  0 default-fixup !
+  postpone ahead postpone [ ; immediate
+: ENDCASE   postpone ] postpone then
+            case-buffer cases @ 3 / for aft
+               dup @ . cell+
+               dup @ . cell+
+               dup @ . cell+ cr
+            then next drop ; immediate
+: OTHERWISE    here default-target ! postpone ] ; immediate
+: OF ( n -- ) case, here case, postpone ] ; immediate
+: ENDOF   postpone [ postpone ahead
+          default-target @ default-fixup @ 0= and
+          if default-fixup ! else case, then ; immediate
+
+forth definitions
+
+: test
+  case
+    1 of ." one" endof
+    2 of ." two" endof
+    3 of ." three" endof
+    otherwise ." other" endof
+  endcase
+;
+
+see test