Questions about functional swift and closures (see content for details)

indirect enum FormExpression {
   case float(Float)
   case reference(String,Int)
   case infix(FormExpression,String,FormExpression)
   case function(String,FormExpression)
}
extension FormExpression {
    static var floatParser:FormParser<FormExpression> {
        return { FormExpression.float($0) }<^>float
    }
 }
infix operator <^> : SequencePrecedence 
func <^><A,B>(lhs:@escaping(A)->B,rhs:FormParser<A>) -> FormParser<B> { 
    return rhs.map(lhs) 
}

it displays an error

Cannot convert value of type"(Float)-> FormExpression" to expected argument type"(_)-> FormExpression"

I tried to modify it several times, also went to Google and Baidu to check, not very ideal, still do not know the solution, I still have some problems in the use of closures. So I hope some friends can solve my problem and tell me why.
my code is for practice, is the source code of functional swift, changed a little.
this is the address of the exercise project: (github.com/objcio/functional-swift) . I changed some code- let float = digit.many1.map {Float (String ($0)!}

Mar.20,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-7c3bab-2ab35.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-7c3bab-2ab35.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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