The source for the grammar is
Richards, Martin, and Colin Whitby-Strevens. BCPL:
the language and its compiler. Cambridge University Press, 1981.,
Chapter 8. The grammar was entered by hand and the adapted to Antlr4.
Afterwards, the script transform.sh, which uses Trash to
remove mutual left recursion, and define an appropriate partition between
lexer and parser.
The examples included we[re gathered from the Internet. The best source is the source for the compiler, bcpl.gtz.
March 14, 2021.