F#: Breaking out of a loop -

i new programming , f# first language.

i have list of urls that, when first accessed, either returned http error 404 or experienced gateway timeout. these urls, try accessing them 3 times. @ end of these 3 attempts, if webexception error still thrown, assume url doesn't exist, , add text file containing of invalid urls.

here code:

let tryaccessingagain (url: string) (numattempts: int) =     async {         attempt = 1 numattempts             try                  let! html = fetchhtmlasync url                 let name = getnamefrompage html                  let id = getidfromurl url                  let newtextfile = file.create(htmldirectory + "\\" + id.tostring("00000") + " " + name.trimend([|' '|]) + ".html")                 use file = new streamwriter(newtextfile)                  file.write(html)                  file.close()                             :? system.net.webexception -> file.appendalltext("g:\user\invalid urls.txt", url + "\n")         } 

i have tested fetchhtmlasync, getnamefrompage , getidfromurl in f# interactive. of them work fine.

if succeed in downloading html contents of url without using 3 attempts, want break out of for-loop immediately. question is: how may so?

use recursion instead of loop:

let rec tryaccessingagain (url: string) (numattempts: int) =     async {         if numattempts > 0             try                  let! html = fetchhtmlasync url                 let name = getnamefrompage html                  let id = getidfromurl url                  let newtextfile = file.create(htmldirectory + "\\" + id.tostring("00000") + " " + name.trimend([|' '|]) + ".html")                 use file = new streamwriter(newtextfile)                  file.write(html)                  file.close()                         | :? system.net.webexception ->                  file.appendalltext("g:\user\invalid urls.txt", url + "\n")                 return! tryaccessingagain url (numattempts-1)         } 

please note not test , there might syntax errors - sorry if

as @ - might want rewrite logging of invalid url this:

let rec tryaccessingagain (url: string) (numattempts: int) =     async {         if numattempts <= 0             file.appendalltext("g:\user\invalid urls.txt", url + "\n")         else             try                  let! html = fetchhtmlasync url                 let name = getnamefrompage html                  let id = getidfromurl url                  let newtextfile = file.create(htmldirectory + "\\" + id.tostring("00000") + " " + name.trimend([|' '|]) + ".html")                 use file = new streamwriter(newtextfile)                  file.write(html)                  file.close()                         | :? system.net.webexception ->                  return! tryaccessingagain url (numattempts-1)         } 

this way logged once attempts made