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linewid = linewid/2;
define begin_group {
[Start: Here;
}
define end_group {
End: Here;] with .Start at Here;
move to last [].End;
}
define terminal {
begin_group();
arrow;
command ".FT TT";
command ".DOC_PT_SIZE +4";
circle $1;
command ".DOC_PT_SIZE -4";
command ".FT R";
line;
end_group();
}
define nonterminal {
begin_group();
arrow;
command ".FT I";
box $1;
command ".FT R";
line;
end_group();
}
define keyword {
begin_group();
arrow;
command ".FT TT";
box $1;
command ".FT R";
line;
end_group();
}
define empty {
begin_group();
# straight line, as long as a box would be
line linewid+boxwid+linewid;
end_group();
}
###
### repeat(block);
### Block must have labels `Start` and `End`.
###
define repeat {
line from $1.End to $1.se - (0,circlerad*2);
arrow to ($1.Start,Here) then to $1.Start;
line from $1.End right linewid/2;
}
###
### repeat(block,terminal_symbol);
###
define repeat_with {
command ".FT TT";
command ".DOC_PT_SIZE +4";
circle at bottom of $1 - (0,circlerad*2) $2;
command ".DOC_PT_SIZE -4";
command ".FT R";
arrow from $1.End to ($1.End,last circle) then \
to east of last circle;
arrow from west of last circle to ($1.Start,last circle .e) then \
to $1.Start;
line from $1.End right linewid/2;
}
### begin_alt(base);
define begin_alt {
line from $1.Start to $1.sw - (0,boxht);
begin_group();
}
### end_alt(base);
define end_alt {
end_group();
# base might be smaller than alternative
if (Here.x < $1.End.x) then {
line to ($1.End,Here);
}
arrow to (Here,$1.End);
# Extend end of base if it is smaller than alternative
# and leave linewid/2 space for next alternative
line from $1.End to Here + (linewid/2,0);
}
define begin_rule {
move down;
right;
command ".FT I";
{$1 at Here - (boxwid/2,0)}
command ".FT R";
begin_group();
line;
}
define end_rule {
arrow;
end_group();
move to last [].sw;
}
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