为什么在函数内用parseExpr执行会报SQL context is not initialized yet

Question

在DolphinDB GUI内执行下面代码：

def yoy_continuous_validation(X, threshold, validation_way, continuous_len){
 if (not(string(validation_way) in ['>','>=','<','<=','='])){
  return NULL
 }
 m = parseExpr("iif(msum(iif(yoy(X)" + iif(string(validation_way) == "=","==",validation_way) + "threshold,1,0),continuous_len) == continuous_len,1,0)").eval()
 return m
}

报错SQL context is not initialized yet，parseExpr拼接的语句为

iif(msum(iif(yoy(X)>threshold,1,0),continuous_len) == continuous_len,1,0)

直接执行不会报错，是什么原因？

Answer 1

如DolphinDB用户手册中所述，parseExpr函数解析变量时，首先搜索会话中的局部变量，再搜索共享变量，但不会搜索函数体内定义的局部变量。这里是因为parseExpr中用到了函数参数变量X的缘故。代码优化可如下所示：

def yoy_continuous_validation(X, threshold, validation_way, continuous_len){
 cmps = [gt, ge, lt, le, eq]
 index = ['>','>=','<','<=','='].find(string(validation_way))
 if(index < 0)  return NULL
 return  int(msum(cmps[index](yoy(X), threshold), continuous_len) == continuous_len)
}