/*
* apply parameters to a lambda
* create a new enviroment block, add all parameter symbol into this enviroment
* then bind parameters with these symbol
* for example we have symbols in upper table: TRUE = \(x,y).x; FALSE = \(x,y).y; AND = \(p,q).p q FALSE;
* then we want to eval "a = AND TRUE FALSE"; we call ApplyToLambda( AND, {TRUE, FALSE}, env)
* what should be done in ApplyToLambda is
* 1. create new enviroment block
* 2. p bind to TRUE; q bind to FALSE
* 3. call ApplyToLambda(p, {q, FALSE}) which is equal to ApplyToLambda(TRUE, {FALSE, FALSE})
* do 1-3 until we meet a terminal symbol
*
*/
private static EnviromentNode ApplyToLambda(string lambdaSymbol, EnviromentNode[] parameters, Enviroment enviroment, Enviroment closure)
{
EnviromentNode lambda = enviroment.LookupSymbol(lambdaSymbol);
if (lambda == null)
throw new Exception("unknow symbol: " + lambdaSymbol);
EvalDelayEvalBlock(lambda);
// bind parameter to enviroment
Enviroment newEnviro = new Enviroment(enviroment);
EnviromentBlock block = new EnviromentBlock();
newEnviro.AddEnviroment(block);
ParseNode paramNodes = null;
if (lambda.GrammerNode.Token.Type != TokenType.LAMBDA)
{
paramNodes = lambda.GrammerNode.Nodes[2];
}
else
{
paramNodes = lambda.GrammerNode;
}
BindParameterToEnviroment(parameters, newEnviro, paramNodes.Nodes[0]);
return EvalDirectFunctionCall(paramNodes.Nodes[1], newEnviro, closure);
}
/*
* when ApplyFunction, do parameter bind like eval lambda, then eval every sentense in function body
* until we met "return"
* if every parameter in parameters[] occures in current enviroment, no need to create new enviroment
*/
static EnviromentNode ApplyFunction(EnviromentNode func, EnviromentNode[] parameters, Enviroment enviroment)
{
// nodes[0] == Symbol
// node[1] == parameters
// node[2] == function body
Enviroment newEnviro = null;
ParseNode paraNode = func.GrammerNode.Nodes[1];
newEnviro = new Enviroment(globalEnviroment);
EnviromentBlock block = new EnviromentBlock();
newEnviro.AddEnviroment(block);
// bind parameter to enviroment
BindParameterToEnviroment(parameters, newEnviro, paraNode);
// eval all body sentense
ParseNode body = func.GrammerNode.Nodes[2];
foreach (ParseNode sentense in body.Nodes)
{
EnviromentNode ret = EvalSentense(sentense, newEnviro);
if (ret != null && ret.Terminate)
{
return ret;
}
}
return null;
}