Function find_expr_key_var

src/ArrayVariable.cpp:101–122

* find the "key" variable of an expression. * return NULL if expression is a function call, constant, or a binary * operation involves at least two variables */

 * operation involves at least two variables
 */
static const Variable* find_expr_key_var(const Expression* e)
{
	if (e->term_type == eVariable) {
		return ((const ExpressionVariable*)e)->get_var();
	}
	else if (e->term_type == eFunction) {
		const ExpressionFuncall* ef = dynamic_cast<const ExpressionFuncall*>(e);
		assert(ef);
		const FunctionInvocation& fi = *(ef->get_invoke());
		if (fi.invoke_type == eBinaryPrim || fi.invoke_type == eUnaryPrim) {
			if (fi.param_value.size()==1) {
				return find_expr_key_var(fi.param_value[0]);
			}
			assert(fi.param_value.size() == 2);
			const Variable* v0 = find_expr_key_var(fi.param_value[0]);
			const Variable* v1 = find_expr_key_var(fi.param_value[1]);
			if (v0 == NULL && v1 != NULL) return v1;
			if (v0 != NULL && v1 == NULL) return v0;
		}
	}
	return NULL;
}

//=======================================================================================
ArrayVariable *