You're right. It appears your code can't find the list_m module. Try
putting it in your lib directory.
On Tuesday, January 13, 2015 at 7:48:13 AM UTC+8, Emacs the Viking wrote:
>
> I am a (not for a while but...) Haskeller but not used to Monads in
> Erlang... I have already made use of the maybe_m monad implementation for
> validating an API JSON request, that's fine, but for some reason my sign-in
> form validation code just meets with a compile error and I can't see why.
> It's late. I should stop!!
>
> Here is the full set of code, then the error...
>
> -module(smsengine_web_controller, [Req]).
> -compile({parse_transform, do}).
> -compile(export_all).
>
> %% @doc The public web controller does not need any authorisation checks.
> before_filters(DefaultFilters, _RequestContext) ->
> utils:no_auth(DefaultFilters).
>
> %% @doc Home page redirect to the template.
> index('GET', []) -> ok.
>
> signin('POST', []) ->
> U = Req:post_param("u"),
> P = Req:post_param("p"),
>
> do([list_m ||
> validate_email(U),
> validate_password(P)
> ]),
>
> {render_other,
> [{controller, "web"}, {action, "index"}],
> []}. %% TODO: session start etc
>
>
> validate_email([]) ->
> list_m:return(100);
> % list_m:return({email_text, "Please supply a valid email address"});
>
> validate_email(_) ->
> list_m:fail([]). %% other validation checks will go here
>
>
> validate_password([]) ->
> list_m:return({password_text, "Please enter your password"});
>
> validate_password(_) ->
> list_m:fail([]). %% other validation checks here
>
> And the error:
>
> [error] Error in controller error undef
> [{list_m,return,"d",[]},{smsengine_web_controller,'-signin/3-fun-1-',3,[{file,"/Users/seancharles/Documents/bitbucket/smsengine/src/controller/smsengine_web_controller.erl"},{line,33}]},{smsengine_web_controller,signin,3,[{file,"/Users/seancharles/Documents/bitbucket/smsengine/src/controller/smsengine_web_controller.erl"},{line,32}]},{boss_web_controller,call_controller_action,3,[{file,"src/boss/boss_web_controller.erl"},{line,363}]},{boss_web_controller,apply_action,4,[{file,"src/boss/boss_web_controller.erl"},{line,355}]},{boss_web_controller,execute_action_inner,9,[{file,"src/boss/boss_web_controller.erl"},{line,334}]},{boss_web_controller_handle_request,process_dynamic_request,4,[{file,"src/boss/boss_web_controller_handle_request.erl"},{line,242}]},{boss_web_controller_handle_request,process_request,4,[{file,"src/boss/boss_web_controller_handle_request.erl"},{line,228}]}]
>
> My intent was to run the list monad over all of the various validation and
> credentials checking functions such that, if all is well I have an empty
> list i.e. the user can redirect to the landing page for their account or,
> if there is at least one error in the list, that I re-display the sign-in
> page and the template shows the errors as and where needed.
>
> It seems to be telling me that the function list_m:return is not defined
> or have I got it wrong??
>
> Thanks and goodnight for now.
> :)
> Sean
>
>
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