struct ast_node*
token_id(char *name)
{
struct ast_node *node;
struct symbol *sym;
switch (current_token) {
case TOKEN_LPARENTH :
node = function_call(name);
break;
case TOKEN_LBRACKET:
node = access_node(name);
break;
default:
sym = symbol_table_lookup_all(name);
if (sym == NULL) {
sym = symbol_new(name, VALUE_TYPE_UNKNOWN);
symbol_table_global_put_symbol(sym);
}
node = (struct ast_node *)ast_node_id(name);
break;
}
return AST_NODE(node);
}
// reset the color of node to G
// return its PREVIOUS color
COLOR ConstraintGraph::erase_color(const GNode & node){
COLOR pre;
GNode & n = access_node(node);
pre=n.color;
n.color = G;
return pre;
}
// add an edge between u,v
bool ConstraintGraph::do_add_edge(const GNode &u,const GNode &v,EType type){
GEdge &uv = access_edge(u,v);
GEdge &vu = access_edge(v,u);
GNode &unode = access_node(u);
GNode &vnode = access_node(v);
if( uv.type == NOEDGE || uv.type == type ){// safely add edge
uv.type = type;
uv.count++;
unode.ecount++;
vu.type = type; // symmetric
vu.count++;
vnode.ecount++;
}
else
report_exit("Trying to add incompatible edge type");
return true;
}
// remove (one) edge between node u,v
// note that when the node becomes standalone, also rip its color
bool ConstraintGraph::remove_edge(const GNode &u,const GNode &v){
GEdge &uv = access_edge(u,v);
GEdge &vu = access_edge(v,u);
GNode &unode = access_node(u);
GNode &vnode = access_node(v);
assert( uv.count == vu.count );
// edge not exist,
if( uv.count == 0 ) return false;
uv.count--;
if( uv.count == 0 ) uv.type = NOEDGE;
unode.ecount--;
if( unode.ecount == 0 ) erase_color(u);
vu.count--; // symmetric
if( vu.count == 0 ) vu.type = NOEDGE;
vnode.ecount--;
if( vnode.ecount == 0 ) erase_color(v);
return true;
}
// try to add edge with color awareness
// return EXIST if the edge exists already
bool ConstraintGraph::add_edge_color(const GNode &u,const GNode &v, EType type)
{
// first check if edge exist
int a=get_node_idx(u);
int b=get_node_idx(v);
//GEdge & uv = access_edge(u,v);
GEdge & uv = edge[a][b];
if( uv.type != NOEDGE ){// already has an edge
if( uv.type != type ) return false; // type incompatible
else do_add_edge(u,v,type); // safely add dummy edge
}
// now we ensure u-v edge NOT exist(NOEDGE)
// check if adding this edge will conflict
// explore all 9 cases: {G,H,V} X {G,H,V}
assert( u != v );
GNode & unode = access_node(u);
GNode & vnode = access_node(v);
COLOR ucolor = get_color(u);
COLOR vcolor = get_color(v);
// node u standalone, which means color = G
if( ucolor == G ){
assert( unode.ecount == 0 );
do_add_edge(u,v,type); // safely add edge
if( vcolor == G ){ // G,G: color them
set_color(unode,HI);
if( type == DIFF ) set_color(vnode,LO);
else set_color(vnode,HI);
}
else if( vcolor == HI ){// G,H
if( type == DIFF ) set_color(unode,LO);
else set_color(unode,HI);
}
else{// G,L
if( type == DIFF ) set_color(unode,HI);
else set_color(unode,LO);
}
return SUCCESS;
}
// v standlone(symmetric to previous case)
else if( vcolor == G ) {
assert( vnode.ecount == 0 );
do_add_edge(v,u,type); // safely add edge
if( ucolor == G ){ // G,G: color them
set_color(unode,LO);
if( type == DIFF ) set_color(vnode,HI);
else set_color(vnode,LO);
}
else if( ucolor == HI ){// H,G
if( type == DIFF ) set_color(vnode,LO);
else set_color(vnode,HI);
}
else{// L,G
if( type == DIFF ) set_color(vnode,HI);
else set_color(vnode,LO);
}
return SUCCESS;
}
else{// u,v not standalone => u,v has colors, but not connected
if( (ucolor != vcolor &&
type == DIFF) || // different color, DIFF edge
(ucolor == vcolor &&
type == SAME)) // same color, SAME edge
{// type compatible
do_add_edge(u,v,type); // safely link them
return SUCCESS;
}
// H-L, H-H or L-L
// try to swap the color
// of one connected component
//ConstraintGraph bak(*this); // make backup
reverse_color(v); // reverse the coloring of v component
COLOR u_newcolor = get_color(u);
if( ucolor != u_newcolor ){
// if u's color changed=>2-color failed
//*this = bak;
return FAIL;
}
else{
do_add_edge(u,v,type);// safely link them
return SUCCESS;
}
}
}