Question

I want to convert some VB.NET code for regular expression to F#.
The following code works in VB.NET:

Dim regOpts As RegexOptions = RegexOptions.IgnoreCase Or RegexOptions.Singleline
Dim r As New Regex("<a[^>]*href\s*=\s*""?(?<HRef>[^"">\s]*)""?[^>]*>", regOpts)

But the corresponding code in F# can not get complied:

open System.Text.RegularExpressions
let regOpts: RegexOptions = RegexOptions.IgnoreCase ||| RegexOptions.Singleline
let reg = new Regex("<a[^>]*href\s*=\s*""?(?<HRef>[^"">\s]*)""?[^>]*>", regOpts)

I got the compiler error:

Error: This value is not a function and cannot be applied

I believe F# does NOT recognize the double quote inside double quote, but for VB.NET, it is OK, my code work correctly. Please show me how to modify the F# code, so it can work.

Answer 1

Just escape the " as \" as described here, instead of the VB.NET escape (that doubles them).

let reg = new Regex("<a[^>]*href\s*=\s*\"?(?<HRef>[^\">\s]*)\"?[^>]*>", regOpts)

Though a better option might be to change it to a verbatim string literal:

let reg = new Regex(@"<a[^>]*href\s*=\s*""?(?<HRef>[^"">\s]*)""?[^>]*>", regOpts)