我用这段代码在文件不存在时报错。
if !File.Exists(inputPath) then
printfn "inputPath doesn't exist %s" inputPath; failwith "stop"结果却出现了这个错误。我哪里理解错了？
error FS0001: This expression was expected to have type
bool ref
but here has type
boolI'm using this code to signal an error if a file is missing.
if !File.Exists(inputPath) then
printfn "inputPath doesn't exist %s" inputPath; failwith "stop"Instead, this error appears. What did I misunderstand?
error FS0001: This expression was expected to have type
bool ref
but here has type
bool在 F# 中 ! 不表示 NOT，而是引用运算符，所以取反要用 not 函数，比如可以写 if not <| File.Exists....
in F#, ! doesn't mean NOT, it's the reference opperator, so negation requires the not function instead, for example you could write if not <| File.Exists....
! 在 F# 中的含义不同，它的定义如下。
type 'a ref { Contents : 'a }
let (!) (cell : ref 'a) = cell.Contents失败是因为你传入了 bool，而 ! 要求的操作数是 bool ref。
改用 not 函数。
if not(File.Exists(inputPath)) then
printfn "inputPath doesn't exist %s" inputPath; failwith "stop"F# gives ! a different meaning, and thats defined as follows:
type 'a ref { Contents : 'a }
let (!) (cell : ref 'a) = cell.ContentsThis fails because you supplied a bool, whereas the operand required by ! is a bool ref.
Replace it with the not function:
if not(File.Exists(inputPath)) then
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