reorganize ex 1.12.5 into correct example and WYSS subsections, plus minor revisions
reorganize ex 1.12.5 into correct example and WYSS subsections, plus minor revisions

tang-junjie/llthw,tang-junjie/llthw,LispTO/llthw,LispTO/llthw,LispTO/llthw,tang-junjie/llthw