Can't parse negatives number in forms

[tonyx]

parse error in forms with decimal.

In Form.fs:

type MyForm = { Value: decimal }

In View.fs

{ Label = "Data"; Html = formInput (fun f -> <@ f.Value @>) [] }

entering a negative number like "-10" lead in the form lead to
"Cound not parse '-10' to Decimal"

workaround by using string, validate them by regexp, and convert the string to decimal

type MyForm = {
Value: string
}

let decimalNumberPattern =  matches  @"-{0,1}\d*(\.{0,1}\d*)" 

let priceAdjustment: Form<PriceAdjustment> = 
    Form ([
        TextProp ((fun f -> <@ f.Value   @>), [decimalNumberPattern])
    ],
[] )