public SEXP evaluate(SEXP expression, Environment rho) {
if (expression instanceof Symbol) {
return evaluateSymbol((Symbol) expression, rho);
} else if (expression instanceof ExpressionVector) {
return evaluateExpressionVector((ExpressionVector) expression, rho);
} else if (expression instanceof FunctionCall) {
return evaluateCall((FunctionCall) expression, rho);
} else if (expression instanceof Promise) {
return expression.force(this);
} else if (expression != Null.INSTANCE && expression instanceof PromisePairList) {
throw new EvalException("'...' used in an incorrect context");
} else {
clearInvisibleFlag();
return expression;
}
}
private SEXP evaluateSymbol(Symbol symbol, Environment rho) {
clearInvisibleFlag();
if (symbol == Symbol.MISSING_ARG) {
return symbol;
}
SEXP value = rho.findVariable(symbol);
if (value == Symbol.UNBOUND_VALUE) {
throw new EvalException(String.format("object '%s' not found", symbol.getPrintName()));
}
if (value instanceof Promise) {
return evaluate(value, rho);
} else {
return value;
}
}
private SEXP evaluateCall(FunctionCall call, Environment rho) {
clearInvisibleFlag();
Function functionExpr = evaluateFunction(call.getFunction(), rho);
return functionExpr.apply(this, rho, call, call.getArguments());
}