不能使用可变变量作为安全函数的参数 [英] Cannot use a mutable variable as an argument of the security function

问题描述

下面的脚本无法编译.
它抛出错误Cannot use a mutable variable as an argument of the security function
我不明白为什么.
我在安全函数中使用的参数不是可变变量.
当我注释掉 h := h * 3 行时，脚本编译正常.
有人知道这里发生了什么吗?
这可能是 Pine 脚本的错误吗?

The script below does not compile.
It throws the error Cannot use a mutable variable as an argument of the security function
I don't understand why.
The arguments I use in the security function are not mutable variables.
When I comment out the line h := h * 3, the script compiles ok.
Does anybody know what's going on here?
Could this be a Pine script bug?

//@version=4
study("My Script")

[h, l, c] = security(syminfo.ticker, "D", [high,low,close], lookahead = barmerge.lookahead_on) // actual daily high,low,close.
h := h * 3 // Commenting this line results removes the error: "Cannot use a mutable variable as an argument of the security function."

plot(h)

推荐答案

出于某种原因，当用户定义的函数返回它们时，解构赋值的处理方式与 security() 时不同做.将您的 security() 调用封装在一个函数中即可:

For some reason, destructured assignments aren't treated the same way when a user-defined function returns them vs when security() does. Encapsulating your security() call in a function will work:

//@version=4
study("")
f_sec() => security(syminfo.tickerid, "D", [high,low,close], lookahead = barmerge.lookahead_on)
[h, l, c] = f_sec()
h := h * 3
plot(h)

请注意，您在使用前瞻时使用的是历史柱的未来数据，而不是像您在那里所做的那样将系列偏移 1.

Note that you are using future data on historical bars when using lookahead and not offsetting the series by 1, as you are doing in there.

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