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* Use a symbol table to represent identifiers and attribute names

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efficiently.  The symbol table ensures that there is only one copy
  of each symbol, thus allowing symbols to be compared efficiently
  using a pointer equality test.
This commit is contained in:
Eelco Dolstra 2010-04-13 12:25:42 +00:00
parent 10e8b1fd15
commit ac1e8f40d4
15 changed files with 228 additions and 101 deletions
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25
src/libexpr/eval-test.cc
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@ -12,7 +12,7 @@ using namespace nix;
void doTest(EvalState & state, string s)
{
Expr * e = parseExprFromString(s, absPath("."));
Expr * e = parseExprFromString(state, s, absPath("."));
std::cerr << ">>>>> " << *e << std::endl;
Value v;
state.eval(e, v);
@ -23,6 +23,29 @@ void doTest(EvalState & state, string s)
void run(Strings args)
{
SymbolTable t;
printMsg(lvlError, format("size of symbol: %1% bytes") % sizeof(Symbol));
Symbol s1 = t.create("foo");
Symbol s2 = t.create("foo");
Symbol s3 = t.create("bar");
Symbol s4 = t.create("foo");
assert(s1 == s2);
assert(s1 == s4);
assert(s1 != s3);
std::map<Symbol, int> m;
m[s1] = 123;
m[s3] = 456;
std::cout << m[s1] << std::endl;
std::cout << m[s2] << std::endl;
std::cout << m[s3] << std::endl;
std::cout << m[s4] << std::endl;
EvalState state;
printMsg(lvlError, format("size of value: %1% bytes") % sizeof(Value));