int Eval()
{
switch (type)
{
case Terminal:
return value;
case Unary:
{
int z = lhs->Eval();
switch (index)
{
case 0: return factorial(z); break;
case 1: return doubleFactorial(z); break;
case 2: return subFactorial(z); break;
case 3:
// square root. really nasty
if (z < 0) return numeric_limits<int>::quiet_NaN(); // fail
else {
float r = sqrtf((float)z);
if (r == floor(r))
return (int)r;
else return numeric_limits<int>::quiet_NaN();
}
}
}
case Binary:
assert(lhs);
assert(rhs);
return binaryFunctions[index](lhs->Eval(), rhs->Eval());
default:
assert(!"Should not be here!");
}
}
void Simplify()
{
if (type == Unary)
{
lhs->Simplify();
auto z = lhs->Eval();
if ((z >= 0 && z <= 5) || z == 48 || z == 720)
{
type = Terminal;
value = z;
delete lhs;
lhs = nullptr;
}
}
else if (type == Binary)
{
lhs->Simplify();
rhs->Simplify();
auto u = lhs->Eval();
if (u >= 0 && u <= 5)
{
type = Terminal;
value = u;
delete lhs;
lhs = nullptr;
}
auto v = rhs->Eval();
if (v >= 0 && v <= 5)
{
type = Terminal;
value = v;
delete rhs;
rhs = nullptr;
}
}
}
int main(int argc, char* argv[]) {
if (argc < 2) {
puts("filename missing.");
return 1;
}
FILE* file = fopen(argv[1], "r");
if (file == NULL) {
fprintf(stderr, "couldn't open: %s\n", argv[1]);
return 1;
}
yyin = file;
Node* root = NULL;
yyparse(root);
// after calling yyparse, the program has been successfully
// parsed and the root of AST is stored in Node* root.
Environment global;
(root->Eval(&global));
fclose(file);
return 0;
}
