. "$BST_LIB"
require byacc byacc/present

# byacc (Berkeley Yacc) reads a yacc grammar spec and emits an LALR(1) C parser.
# The recipe renames the installed binary to "byacc" (--program-transform-name).
# Drive it on a minimal grammar in a scratch dir — byacc writes y.tab.c into the
# current directory, so run it from there.
work=${TMPDIR:-/tmp}/bst-byacc.$$
rm -rf "$work"; mkdir -p "$work"
cat > "$work/calc.y" <<'YACC'
%token NUM
%%
expr : NUM
     | expr '+' NUM
     ;
%%
YACC

# -d emits the parser (y.tab.c) and the token header (y.tab.h).
( cd "$work" && byacc -d calc.y ) >"$work/byacc.log" 2>&1; rc=$?

# The C parser source is produced and byacc exits 0.
if [ "$rc" -eq 0 ] && [ -f "$work/y.tab.c" ]; then bst_ok byacc/generate
else bst_notok byacc/generate "rc=$rc $(_bst_1line "$(cat "$work/byacc.log" 2>&1)")"; fi

# The generated parser carries the yacc driver routine yyparse().
check_out byacc/parser "yyparse" cat "$work/y.tab.c"

# -d wrote the token header with a #define for the declared token.
check_out byacc/defines "NUM" cat "$work/y.tab.h"

rm -rf "$work"