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Parse Error On Input Where


You have a lot of redundant parentheses: drop ((length pack)-1) can be simply drop (length pack - 1). permalinkembedsavegive gold[–]zeltol[S] 0 points1 point2 points 2 years ago(4 children)Can you please explain why tabs and spaces make a difference? What I need is to use an if condition inside a do block. Prove a geometry question about angles and radii in five collinear circles? his comment is here

It might help a little bit if you better explained what you are trying to do, or what you expect to be happening with the code you wrote. Recalll is crowed sourced knowledge vault, where community can create, curate and access qualitative knowledge, In form of small and precise topics. You need to provide an value, if you're coming from Python, then think about something like a = "dogs" if 1 < 0 else "cats" here, you need to provide the A simple example: howMany :: [a] -> String howMany [] = "Zero" howMany [x] = "One" howMany (x:xs) = "Many" Haskell functions can be defined with a sequence of "equations" like

Parse Error On Input Where

See also: Haskell “where” indentation: why must it be indented past identifier? permalinkembedsaveparentgive gold[–]bss03 4 points5 points6 points 2 years ago(1 child)Not just GHC. How to proceed in light of peer-review confidentiality? Absolutely fine, IMO.

  1. View More Recalll - Medium for programmers.
  2. foo : bar) in other languages.
  3. Would Voldemort have succeeded if he simply ignored the prophecy?
  4. spaces.
  5. Is there any way to fix this without completely revamping the logic?
  6. share|improve this answer answered Aug 5 '12 at 14:12 Niccolo M. 1,615622 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google
  7. Truth Stone: Effects on the justice system, and criminal world What computer information can WiFi networks see?
  8. The question is about where rather than do, but the general principle is the same, and the answers there cover it well.
  9. Here, one coder attempted to write a function hanoi to solve the Towers of Hanoi problem, but to code it so that each tower could be named polymorphically, using, for example,
  10. share|improve this answer edited Mar 23 '12 at 19:20 answered Mar 23 '12 at 19:12 ehird 34.7k2148168 Thank you for this, it seems like an intelligent solution and bonus

Privacy policy About HaskellWiki Disclaimers Search: LoginHelp/GuideAbout TracPreferencesRegister WikiTimelineRoadmapBrowse SourceView TicketsSearchBlog Context Navigation ← Previous TicketNext Ticket → GHC Trac Home GHC Home   Joining In Report a bug Newcomers info Can droids be shut down manually? Join them; it only takes a minute: Sign up “parse error on input” in Haskell if-then-else conditional up vote 2 down vote favorite The following do block throws the error "parse An example of how this might cause trouble is as follows: Although the two lines wherebmi = ... skinny = ...

There are other ways of iterating over lists as well. Haskell If Then Else GHC 7.0.1 and later). 1.2 If / Then / Else if-then statements must always include an 'else' portion. This means you have to be more disciplined with tabs vs. There can only be one expression after the = sign, but you have provided two, separated by a newline.

main = do contents <- BL.getContents let myData = decode contents :: Maybe Data if maybe True (\x -> result x /= "success") myData then error ("JSON download failed") else let For that reason, you can't omit the else, much in the same way that you can't when using the ternary if operator (conditon ? This doesn't work in Haskell, you must instead of the conditional inside the assignment of the binding like so: [ t | let e = [], let o = p!!14, r bmiTell :: ( RealFloat a) => a -> a -> String bmiTell weight height |bmi <= skinny = "Underweight" |bmi <= 20 = "Normal" |bmi <= 25 = "Overweight" |otherwise =

Haskell If Then Else

You won't be able to vote or comment. 567Beginner - Parse Error on Input '=' (self.haskell)submitted 2 years ago * by zeltolI am studying from Learn You a Haskell for Greater Good. One should also recognize that the types returned by the then and else branches must match due to Haskell's strong and static type system. Parse Error On Input Where more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed A word for "to be physically removed from" Why are there separate seasons for Archery and Firearm hunting for deer?

How to jump to middle of buffer Magic popcount numbers In how many ways can a given planar graph be mapped into the plane? How to toggle Show/Hide hidden files in Windows through command line? It's arguably allowed to have tab stops at 4,12,20,etc. Physical interpretation of circuit with battery charging capacitor Why do people call him Red?

To avoid any confusion I'm not using tabs at all anymore. Haskell layout rules specify that tab stops are 8 columns apart and that the tab character moves to the next tab stop. permalinkembedsaveparentgive gold[–]yitz 1 point2 points3 points 2 years ago(1 child)From experience, tabs are a recipe for disaster. Loading trait on weapons without ammunition What is a more effective shield for magnetic fields between 300 and 500kHz Solid copper or copper mesh?

Is there a way to find out if my living room ceiling has insulation? look like they're aligned in your text editor (which probably uses 4-space tabs), as far as GHC is concerned what you actually have is wherebmi = ... < tab >< tab A world with a special political system Microwaving a glass of water, what happens?

perfect explanation! –DemianArdus May 5 '14 at 2:10 add a comment| up vote 2 down vote You're missing an else.

x = b? Another way of writing hanoi_shower, using map, is as follows: hanoi_shower :: Show a => [(a, a)] -> String hanoi_shower moves = unlines (map move moves) where move (a, b) = You have two different definitions for fractionalKnapsack, each taking a different number of arguments, clearly that causes the compiler some trouble. Bank claims I'm personally liable for small business fees; despite leaving the company?

ignoring the list indexing and use of length) would be (using guards): let firstPos = position !! 1 newPack | firstPos == 0 = drop (length pack - 1) pack | share|improve this answer edited May 5 '14 at 0:26 answered May 5 '14 at 0:24 Edgar Aroutiounian 2,72051429 add a comment| up vote 2 down vote In Haskell everything after = All of the statements in a do block must start with the exact same whitespace, and not just appear to line up visually. check over here Since the line bmi = weight / (height^2) skinny = ...

Rather than using if length (x:xs) <= 1 howMany :: [a] -> String howMany [] = "Zero" howMany [x] = "One" howMany (x:xs) = "Many" Haskell functions can be defined with sgetLine = do x <- getChar if x == '\n' then do putChar x return [] else do putChar '_' xs <- sgetLine return (x:xs) The lines in within a do The problem is how to iterate over the elements (pairs) of the list while separating the first a of each pair from the second a. Is it worth sending a manned mission to a black hole?

For example a missing else clause now prints "parse error in if statement: else clause empty" instead of "parse error (possibly incorrect indentation or mismatched brackets)". Daily news and info about all things Haskell related: practical stuff, theory, types, libraries, jobs, patches, releases, events and conferences and more... Not the answer you're looking for? How to toggle Show/Hide hidden files in Windows through command line?

It's unlikely that your text editor and GHC agree on how many spaces each tab should count as, so if you mix tabs and spaces things that look fine to you You need to either follow the indentation rules or use explicit braces and semicolons (as in your second code block). Most likely to do with the "where"-clause. haskell indentation share|improve this question edited Aug 7 '15 at 3:47 duplode 11.7k22246 asked Aug 7 '15 at 3:14 matthias 32217 add a comment| 2 Answers 2 active oldest votes up

palin :: IO () palin = do line <- getLine putStr line --Probably better to use putStrLn? This was the primary problem, though. Here is a corrected version of the code above: hanoi_shower :: Show a => [(a, a)] -> String hanoi_shower moves = unlines ["Move " ++ show a ++ " to "++ All rights reserved.REDDIT and the ALIEN Logo are registered trademarks of reddit inc.πRendered by PID 32333 on app-576 at 2016-12-01 23:04:20.670923+00:00 running 1352202 country code: IE.

Join them; it only takes a minute: Sign up Haskell parse error on input 'if'? asked 3 years ago viewed 1778 times active 3 years ago Blog How Do Software Developers in New York, San Francisco, London and Bangalore… Linked 0 Haskell: if-then-else parse error Related deleting billions of files from directory while seeing the progress as well A word for "to be physically removed from" Are DIY store bolts okay for critical components? One has 1 argument, the other has 2.

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