F# less than operator in pattern matching -

for reason less operator in pattern match not work. it's error have , it's driving me insane. i'm missing obvious appreciated.

let checkaccount account =  match account | {balance < 10.00} -> console.writeline("balance low") | {balance >= 10.00 , <= 100.00} -> console.writeline("balance ok") | {balance > 100.00} -> console.writeline("balance high") 

this type:

type account = {accountnumber:string              mutable balance:float}              member this.withdraw(amnt:float) =                  if amnt > this.balance                     console.writeline("unable withdraw. amount wish withdraw greater current balance.")                 else                     this.balance <- this.balance - amnt                     console.writeline("you have withdrawn £" + amnt.tostring() + ". balance now: £" + this.balance.tostring())             member this.deposit(amnt:float) =                 this.balance <- this.balance + amnt                 console.writeline("£" + amnt.tostring() + " deposited. new balance is: £" + this.balance.tostring())             member this.print =                  console.writeline("account number: " + this.accountnumber)                 console.writeline("balance: £" + this.balance.tostring()) 

you can use pattern matching extract balance value, bind new name , compare values using when clause:

let checkaccount account =    match account   | {balance = b} when b < 10.00 -> console.writeline("balance low")   | {balance = b} when b >= 10.00 && b <= 100.00 -> console.writeline("balance ok")   | {balance = b} when b > 100.00 -> console.writeline("balance high") 

i in case, not getting using pattern matching. if wrote same code using if, nicer.

you can use bit fancier approach , define active patterns let compare values:

let (|lessthan|_|) k value = if value < k some() else none let (|morethan|_|) k value = if value > k some() else none 

then can use instead:

let checkaccount account =    match account   | {balance = lessthan 10.0} -> console.writeline("balance low")   | {balance = lessthan 100.0 & morethan 10.0 } -> console.writeline("balance ok") 

this interesting - because can use & construct combine multiple active patterns in lessthan 100.0 & morethan 10.0.