types - Haskell, String vs ...String? -


i'm following happstack lite tutorial website. http://happstack.com/page/view-page-slug/9/happstack-lite-tutorial

right now, i'm implementing echo function, , compiler giving me error message don't understand. here's code:

echo :: serverpart response echo =     path $ \(msg :: string) ->         ok $ template "echo" $             h1 "echo service"             p "giant, haskell style papagallo"             p msg

and here's error message:

src/motiondude.hs:35:15:     couldn't match type `[char]' `text.blaze.internal.markupm ()'     expected type: html       actual type: string     in first argument of `p', namely `msg'     in stmt of 'do' block: p msg     in second argument of `($)', namely       `do { h1 "echo service";             p "giant, haskell style papagallo";             p msg }'

i thought quote-enclosed "thing", 

"giant, haskell style papagallo"

was string. yet, understand compiler error, p not accept string argument. can explain me?

the problem seem have enabled overloadedstring extensions means 

"foo" :: isstring =>

to coerce plain old string implementing isstring use fromstring. in case however, happstack has function html looks more appropriate.


Comments

Post a Comment

Popular posts from this blog

user interface - How to replace the Python logo in a Tkinter-based Python GUI app? -

is there way change default logo, python logo , appears in window's task bar? notice have replaced default tk logo used appear in application window. i using windows 7 , python 2.6 , developing gui of tkinter. you can using winico tk extension package. winico package can used add system tray icons tk programs. the following sample shows 1 way change runtime application icon. note need provide .ico file suitable sizes of icons in on command line , need use pythonw. not change taskbar icon console when running python script. test extracted winico0.6 package python\tcl\winico0.6 folder package require winico work , ran code below using pythonw winico_test.py path\to\some\ico\file.ico . import sys tkinter import * def main(argv): root = tk() root.update() root.tk.call('package','require','winico') id = root.tk.call('winico','createfrom',argv[1]) root.tk.call('winico','setwindow',root,id...
Read more

objective c - Greedy NSProgressIndicator Allocation -

i'm using bunch of nsprogressindicators @ once (32 exact) , looks when they're animating start allocating memory no one's business greedy_run http://i62.tinypic.com/15rgmso.png i've got reports app slowdown , crash after days of uptime, , looks culprit, it's hard pinpoint bugs take days appear. i comment out call start animating, memory behaves expected. result of multiple nsprogressindicators alloc'ed on same thread? or maybe sandboxing? of constant allocations coming core animation threads, don't know else going on. custom nsview progress indicator lives in @interface myview () @property (nonatomic, strong) nsimageview *imageview; @property (nonatomic, strong) nstextview *numbertxt; @property (nonatomic, strong) nsprogressindicator *progress; @end @implementation myview - (id)initwithframe:(nsrect)framerect { self = [super initwithframe:framerect]; if (self) { // image nsimage *image = [nsimage imagenamed:@"bg.png"]; c...
Read more

how to set an OCR language in Google Drive -

i need upload image google drive including ocr feature. the problem setocrlanguage method. need specify hebrew language , based on iso 639-1 codes should "heb". i'm getting response "code" : 400, "errors" : [ { "domain" : "global", "location" : "ocrlanguage", "locationtype" : "parameter", "message" : "invalid value", "reason" : "invalid" } ], any idea should code or can list of avaliable codes?
Read more