notes: some notes about the implementation of cmdgroup

NOTES.md

@@ -207,6 +207,29 @@ not remain in effect after the subshell completes.
 
 The exit status of this construct is the exit status of LIST.
 
+```c
+struct s_cmdgroup;
+
+typedef union u_cmdgroup_item_inner 
+{
+	struct s_cmdgroup cmdgroup;
+	struct s_cmdlist  cmdlist;
+}	t_cmdgroup_item_inner;
+
+typedef struct s_cmdgroup_item
+{
+	enum e_cmdgroup_item_type 	type;
+	union u_cmdgroup_item_inner inner;
+}	t_cmdgroup_item;
+
+typedef struct s_cmdgroup
+{
+	int 					item_num;
+	struct s_cmdgroup_item 	*items;
+	struct s_redirects		*redirections;
+}	t_cmdgroup;
+```
+
 ### Shell Expansion
 
 cf. 3.5 Shell Expansions
@@ -389,6 +412,48 @@ bash-5.1$ echo "hello world" > $nonexist
 bash: $nonexist: ambiguous redirect
 ```
 
+Interesting cases:
+command group must handle redirections at the scale of the group
+pipelines handle piplines
+simple commands handle its own file redirections
+group redirections may not appear at the start, except for here_doc, which will give a parse error *afterwards*
+```shell
+bash-5.2$ (echo hello | cat -e > outcat && echo hi) > outgroup
+bash-5.2$ cat outgroup 
+hi
+bash-5.2$ cat outcat 
+hello$
+bash-5.2$ (echo hello | cat -e && echo hi) > outgroup2
+bash-5.2$ cat outgroup2
+hello$
+hi
+bash-5.2$ (echo hello > outhello | cat -e && echo hi) > outgroup3
+bash-5.2$ cat outhello
+hello
+bash-5.2$ cat outgroup3
+hi
+bash-5.2$ > outgroup4 (echo hello > outhello | cat -e && echo hi)
+bash: syntax error near unexpected token `('
+bash-5.2$ echo bonjour > infile
+bash-5.2$ < infile (cat - > outhello | cat -e && echo hi)
+bash: syntax error near unexpected token `('
+bash-5.2$ << EOF (cat - > outhello | cat -e && echo hi)
+> hello
+> EOF
+bash: syntax error near unexpected token `('
+bash-5.2$ (cat - > outhello | cat -e && echo hi) < infile
+hi
+bash-5.2$ (cat - > outhello | cat -e && echo hi) << EOF
+> helllo
+> EOF
+hi
+bash-5.2$ cat outhello 
+helllo
+bash-5.2$ (echo coucou | echo hello) > outfile 
+bash-5.2$ cat outfile 
+hello
+```
+
 #### Here Documents
 cf. Bash Reference Manual 3.6.6 Here Documents