From 5f45319d577e1ef8a0d28f08fd37a7ed76433958 Mon Sep 17 00:00:00 2001 From: Devin McGinty Date: Sat, 31 Jan 2015 19:40:55 -0500 Subject: Add more information on ranges in Haskell --- haskell.html.markdown | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 748a29da..d5dd5141 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -67,10 +67,18 @@ not False -- True ---------------------------------------------------- -- Every element in a list must have the same type. --- Two lists that are the same +-- These two lists are the same [1, 2, 3, 4, 5] [1..5] +-- Ranges are versatile. +['A'..'F'] -- "ABCDEF" + +-- You can create a step in a range. +[0,2..10] -- [0, 2, 4, 6, 8, 10] +[5..1] -- This doesn't work because Haskell defaults to incrementing. +[5,4..1] -- [5, 4, 3, 2, 1] + -- You can also have infinite lists in Haskell! [1..] -- a list of all the natural numbers -- cgit v1.2.3 From 411b2b01d3a83369f0754ec03b40499e4f8bcade Mon Sep 17 00:00:00 2001 From: Devin McGinty Date: Sun, 1 Feb 2015 16:39:52 -0500 Subject: Add example of string-as-list and fix punctuation --- haskell.html.markdown | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index d5dd5141..52433aaa 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -59,6 +59,7 @@ not False -- True "Hello " ++ "world!" -- "Hello world!" -- A string is a list of characters +['H', 'e', 'l', 'l', 'o'] -- "Hello" "This is a string" !! 0 -- 'T' @@ -67,7 +68,7 @@ not False -- True ---------------------------------------------------- -- Every element in a list must have the same type. --- These two lists are the same +-- These two lists are the same: [1, 2, 3, 4, 5] [1..5] -- cgit v1.2.3 From 36a296de5d8d82212755ba33388517486f7f804c Mon Sep 17 00:00:00 2001 From: Zach Munro-Cape Date: Sun, 1 Mar 2015 15:16:29 -0400 Subject: Moved explanation of indexing into a list earlier This way, it is clear what [1..] !! 999 means later on. --- haskell.html.markdown | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 52433aaa..79fbf09f 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -80,6 +80,9 @@ not False -- True [5..1] -- This doesn't work because Haskell defaults to incrementing. [5,4..1] -- [5, 4, 3, 2, 1] +-- indexing into a list +[0..] !! 5 -- 5 + -- You can also have infinite lists in Haskell! [1..] -- a list of all the natural numbers @@ -99,9 +102,6 @@ not False -- True -- adding to the head of a list 0:[1..5] -- [0, 1, 2, 3, 4, 5] --- indexing into a list -[0..] !! 5 -- 5 - -- more list operations head [1..5] -- 1 tail [1..5] -- [2, 3, 4, 5] -- cgit v1.2.3 From 4e00fa4734bd39436f3336b4ce1034b65c265657 Mon Sep 17 00:00:00 2001 From: Cornel Punga Date: Mon, 16 Mar 2015 21:09:17 +0200 Subject: Update haskell.html.markdown. Wrong explanation about '$' operator --- haskell.html.markdown | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 79fbf09f..d5dfd122 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -202,9 +202,9 @@ foo = (*5) . (+10) foo 5 -- 75 -- fixing precedence --- Haskell has another function called `$`. This changes the precedence --- so that everything to the left of it gets computed first and then applied --- to everything on the right. You can use `$` (often in combination with `.`) +-- Haskell has another function called `$`. Anything appearing after it will +-- take precedence over anything that comes before. +-- You can use `$` (often in combination with `.`) -- to get rid of a lot of parentheses: -- before -- cgit v1.2.3 From 9fb21f1ce4c02e8cad50046f90d026ccab284626 Mon Sep 17 00:00:00 2001 From: Cornel Punga Date: Mon, 16 Mar 2015 21:24:21 +0200 Subject: Haskell.html.markdown. Wrong result of an expression. The seventh Fibonacci number is 13 (odd number), so the result of 'even 13' is false. --- haskell.html.markdown | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index d5dfd122..f1025d44 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -208,13 +208,13 @@ foo 5 -- 75 -- to get rid of a lot of parentheses: -- before -(even (fib 7)) -- true +(even (fib 7)) -- false -- after -even . fib $ 7 -- true +even . fib $ 7 -- false -- equivalently -even $ fib 7 -- true +even $ fib 7 -- false ---------------------------------------------------- -- 5. Type signatures -- cgit v1.2.3 From a81affb3027b81aa16eba8cac159a18081cff449 Mon Sep 17 00:00:00 2001 From: Geoff Liu Date: Mon, 16 Mar 2015 14:07:19 -0600 Subject: Make the two fib functions consistent --- haskell.html.markdown | 36 ++++++++++++++++++------------------ 1 file changed, 18 insertions(+), 18 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 79fbf09f..2f807c5f 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -148,12 +148,12 @@ add 1 2 -- 3 -- Guards: an easy way to do branching in functions fib x - | x < 2 = x + | x < 2 = 1 | otherwise = fib (x - 1) + fib (x - 2) -- Pattern matching is similar. Here we have given three different -- definitions for fib. Haskell will automatically call the first --- function that matches the pattern of the value. +-- function that matches the pattern of the value. fib 1 = 1 fib 2 = 2 fib x = fib (x - 1) + fib (x - 2) @@ -181,7 +181,7 @@ foldl1 (\acc x -> acc + x) [1..5] -- 15 ---------------------------------------------------- -- partial application: if you don't pass in all the arguments to a function, --- it gets "partially applied". That means it returns a function that takes the +-- it gets "partially applied". That means it returns a function that takes the -- rest of the arguments. add a b = a + b @@ -319,13 +319,13 @@ Nothing -- of type `Maybe a` for any `a` -- called. It must return a value of type `IO ()`. For example: main :: IO () -main = putStrLn $ "Hello, sky! " ++ (say Blue) +main = putStrLn $ "Hello, sky! " ++ (say Blue) -- putStrLn has type String -> IO () --- It is easiest to do IO if you can implement your program as --- a function from String to String. The function +-- It is easiest to do IO if you can implement your program as +-- a function from String to String. The function -- interact :: (String -> String) -> IO () --- inputs some text, runs a function on it, and prints out the +-- inputs some text, runs a function on it, and prints out the -- output. countLines :: String -> String @@ -339,43 +339,43 @@ main' = interact countLines -- the `do` notation to chain actions together. For example: sayHello :: IO () -sayHello = do +sayHello = do putStrLn "What is your name?" name <- getLine -- this gets a line and gives it the name "name" putStrLn $ "Hello, " ++ name - + -- Exercise: write your own version of `interact` that only reads -- one line of input. - + -- The code in `sayHello` will never be executed, however. The only --- action that ever gets executed is the value of `main`. --- To run `sayHello` comment out the above definition of `main` +-- action that ever gets executed is the value of `main`. +-- To run `sayHello` comment out the above definition of `main` -- and replace it with: -- main = sayHello --- Let's understand better how the function `getLine` we just +-- Let's understand better how the function `getLine` we just -- used works. Its type is: -- getLine :: IO String -- You can think of a value of type `IO a` as representing a --- computer program that will generate a value of type `a` +-- computer program that will generate a value of type `a` -- when executed (in addition to anything else it does). We can --- store and reuse this value using `<-`. We can also +-- store and reuse this value using `<-`. We can also -- make our own action of type `IO String`: action :: IO String action = do putStrLn "This is a line. Duh" - input1 <- getLine + input1 <- getLine input2 <- getLine -- The type of the `do` statement is that of its last line. - -- `return` is not a keyword, but merely a function + -- `return` is not a keyword, but merely a function return (input1 ++ "\n" ++ input2) -- return :: String -> IO String -- We can use this just like we used `getLine`: main'' = do putStrLn "I will echo two lines!" - result <- action + result <- action putStrLn result putStrLn "This was all, folks!" -- cgit v1.2.3 From 2f43da109ffab5a4d3dd582cc51a7c3d95dd4987 Mon Sep 17 00:00:00 2001 From: Cornel Punga Date: Wed, 25 Mar 2015 18:08:32 +0200 Subject: [haskell.html.markdown] Changed explanation for Haskell '$' operator --- haskell.html.markdown | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index f1025d44..6bdc78e0 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -202,10 +202,12 @@ foo = (*5) . (+10) foo 5 -- 75 -- fixing precedence --- Haskell has another function called `$`. Anything appearing after it will --- take precedence over anything that comes before. --- You can use `$` (often in combination with `.`) --- to get rid of a lot of parentheses: +-- Haskell has another operator called `$`. This operator applies a function +-- to a given parameter. In contrast to standard function application, which +-- has highest possible priority of 10 and is left-associative, the `$` operator +-- has priority of 0 and is right-associative. Such a low priority means that +-- all other operators on both sides of `$` will be evaluated before applying +-- the `$`. -- before (even (fib 7)) -- false -- cgit v1.2.3 From e8a1ee8912d1c9bb0145c2afbdc530463fc612b7 Mon Sep 17 00:00:00 2001 From: Cornel Punga Date: Fri, 27 Mar 2015 15:25:33 +0200 Subject: [haskell.html.markdown] Explanation for Haskell '$' operator with support from @geoffliu --- haskell.html.markdown | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 6bdc78e0..6c98c2b6 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -205,9 +205,8 @@ foo 5 -- 75 -- Haskell has another operator called `$`. This operator applies a function -- to a given parameter. In contrast to standard function application, which -- has highest possible priority of 10 and is left-associative, the `$` operator --- has priority of 0 and is right-associative. Such a low priority means that --- all other operators on both sides of `$` will be evaluated before applying --- the `$`. +-- has priority of 0 and is right-associative. Such a low priority means that +-- the expression on its right is applied as the parameter to the function on its left. -- before (even (fib 7)) -- false -- cgit v1.2.3 From 745ce28d7e72a1de6a1a386f91f8fcae0c99b324 Mon Sep 17 00:00:00 2001 From: Tiddo Langerak Date: Mon, 27 Apr 2015 10:16:16 +0200 Subject: Fixed haskell foldr example For #1068 --- haskell.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index f28fcfe7..6a64442f 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -282,7 +282,7 @@ foldl (\x y -> 2*x + y) 4 [1,2,3] -- 43 foldr (\x y -> 2*x + y) 4 [1,2,3] -- 16 -- This is now the same as -(2 * 3 + (2 * 2 + (2 * 1 + 4))) +(2 * 1 + (2 * 2 + (2 * 3 + 4))) ---------------------------------------------------- -- 7. Data Types -- cgit v1.2.3 From 8544847845c0405e54acadf5125edc0554d73b75 Mon Sep 17 00:00:00 2001 From: ven Date: Mon, 6 Jul 2015 10:40:05 +0200 Subject: change haskell's operator `$` description wording for #1161 --- haskell.html.markdown | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 6a64442f..369b1b20 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -209,14 +209,15 @@ foo 5 -- 75 -- the expression on its right is applied as the parameter to the function on its left. -- before -(even (fib 7)) -- false - --- after -even . fib $ 7 -- false +even (fib 7) -- false -- equivalently even $ fib 7 -- false +-- composing functions +even . fib $ 7 -- false + + ---------------------------------------------------- -- 5. Type signatures ---------------------------------------------------- -- cgit v1.2.3 From a76be91a2d45c7c4a834c2ad6d5164ac907c1038 Mon Sep 17 00:00:00 2001 From: Greg Yang Date: Tue, 20 Oct 2015 12:05:16 -0700 Subject: modify function composition example --- haskell.html.markdown | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 369b1b20..c6d97496 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -195,11 +195,11 @@ foo 5 -- 15 -- function composition -- the (.) function chains functions together. -- For example, here foo is a function that takes a value. It adds 10 to it, --- multiplies the result of that by 5, and then returns the final value. -foo = (*5) . (+10) +-- multiplies the result of that by 4, and then returns the final value. +foo = (*4) . (+10) --- (5 + 10) * 5 = 75 -foo 5 -- 75 +-- (5 + 10) * 4 = 75 +foo 5 -- 60 -- fixing precedence -- Haskell has another operator called `$`. This operator applies a function -- cgit v1.2.3 From 18edced524b790fe3e6c9bb5f69507ca1bfb0553 Mon Sep 17 00:00:00 2001 From: Greg Yang Date: Tue, 20 Oct 2015 12:10:01 -0700 Subject: update the comment in as well --- haskell.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index c6d97496..e3b29937 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -198,7 +198,7 @@ foo 5 -- 15 -- multiplies the result of that by 4, and then returns the final value. foo = (*4) . (+10) --- (5 + 10) * 4 = 75 +-- (5 + 10) * 4 = 40 foo 5 -- 60 -- fixing precedence -- cgit v1.2.3 From f0bbebe789e310ecd76fcfdfa334291928591fb7 Mon Sep 17 00:00:00 2001 From: Greg Yang Date: Tue, 20 Oct 2015 12:10:50 -0700 Subject: really update the comment --- haskell.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index e3b29937..08611e63 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -198,7 +198,7 @@ foo 5 -- 15 -- multiplies the result of that by 4, and then returns the final value. foo = (*4) . (+10) --- (5 + 10) * 4 = 40 +-- (5 + 10) * 4 = 60 foo 5 -- 60 -- fixing precedence -- cgit v1.2.3 From f6b8b079b49a1fcfdc6143fc51bc5d3738ade8f0 Mon Sep 17 00:00:00 2001 From: Patrik Jansson Date: Fri, 23 Oct 2015 23:31:10 +0200 Subject: Some minor fixes I just noted that the example claiming that (add 10) is the same as (+10) was wrong. (A detail - it should be (10+) to match the argument order.) Then I just continued down making a few similar fixes and terminology updates. /Patrik PS. I've been teaching [Advanced Functional Programming](http://www.cse.chalmers.se/edu/course/afp/) (in Haskell) for a few years at Chalmers. --- haskell.html.markdown | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 08611e63..2f58b357 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -189,16 +189,16 @@ foo = add 10 -- foo is now a function that takes a number and adds 10 to it foo 5 -- 15 -- Another way to write the same thing -foo = (+10) +foo = (10+) foo 5 -- 15 -- function composition -- the (.) function chains functions together. -- For example, here foo is a function that takes a value. It adds 10 to it, -- multiplies the result of that by 4, and then returns the final value. -foo = (*4) . (+10) +foo = (4*) . (10+) --- (5 + 10) * 4 = 60 +-- 4*(10 + 5) = 60 foo 5 -- 60 -- fixing precedence @@ -222,7 +222,7 @@ even . fib $ 7 -- false -- 5. Type signatures ---------------------------------------------------- --- Haskell has a very strong type system, and everything has a type signature. +-- Haskell has a very strong type system, and every valid expression has a type. -- Some basic types: 5 :: Integer @@ -259,7 +259,7 @@ case args of _ -> putStrLn "bad args" -- Haskell doesn't have loops; it uses recursion instead. --- map applies a function over every element in an array +-- map applies a function over every element in a list map (*2) [1..5] -- [2, 4, 6, 8, 10] @@ -279,7 +279,7 @@ foldl (\x y -> 2*x + y) 4 [1,2,3] -- 43 -- This is the same as (2 * (2 * (2 * 4 + 1) + 2) + 3) --- foldl is left-handed, foldr is right- +-- foldl is left-handed, foldr is right-handed foldr (\x y -> 2*x + y) 4 [1,2,3] -- 16 -- This is now the same as @@ -318,7 +318,7 @@ Nothing -- of type `Maybe a` for any `a` -- it is not hard to explain enough to get going. -- When a Haskell program is executed, `main` is --- called. It must return a value of type `IO ()`. For example: +-- called. It must return a value of type `IO a` for some type `a`. For example: main :: IO () main = putStrLn $ "Hello, sky! " ++ (say Blue) @@ -361,7 +361,7 @@ sayHello = do -- You can think of a value of type `IO a` as representing a -- computer program that will generate a value of type `a` -- when executed (in addition to anything else it does). We can --- store and reuse this value using `<-`. We can also +-- name and reuse this value using `<-`. We can also -- make our own action of type `IO String`: action :: IO String @@ -417,7 +417,7 @@ Hello, Friend! There's a lot more to Haskell, including typeclasses and monads. These are the big ideas that make Haskell such fun to code in. I'll leave you with one final -Haskell example: an implementation of quicksort in Haskell: +Haskell example: an implementation of a quicksort variant in Haskell: ```haskell qsort [] = [] -- cgit v1.2.3 From b5cb14703ac99e70ecd6c1ec2abd9a2b5dbde54d Mon Sep 17 00:00:00 2001 From: Niko Weh Date: Sat, 31 Oct 2015 19:44:04 +1000 Subject: Haskell: Fix !! operator - Use a finite list, as infinite lists are not introduced yet - Use a list starting from 1 instead of 0, to make it obvious that the element returned comes from the list (and is not the second argument to !!). --- haskell.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 08611e63..936744a0 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -81,7 +81,7 @@ not False -- True [5,4..1] -- [5, 4, 3, 2, 1] -- indexing into a list -[0..] !! 5 -- 5 +[1..10] !! 3 -- 4 -- You can also have infinite lists in Haskell! [1..] -- a list of all the natural numbers -- cgit v1.2.3 From 608615360c7f49cb33c9e7eb3957e031b9b8a89c Mon Sep 17 00:00:00 2001 From: Niko Weh Date: Sat, 31 Oct 2015 22:37:13 +1000 Subject: [haskell/en] Extended section on GHCi - Added the :i command, as i feel that it is as useful as :t. - Added another example for :t, hopefully showcasing it's flexibility - For consistency, changed the name of (.) from function to operator (as is already the case with ($)), and added a short remark in the GHCi section that (most) operators are also functions. --- haskell.html.markdown | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 936744a0..940cf4c7 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -193,7 +193,7 @@ foo = (+10) foo 5 -- 15 -- function composition --- the (.) function chains functions together. +-- the operator `.` chains functions together. -- For example, here foo is a function that takes a value. It adds 10 to it, -- multiplies the result of that by 4, and then returns the final value. foo = (*4) . (+10) @@ -401,11 +401,26 @@ main'' = do let foo = 5 --- You can see the type of any value with `:t`: +-- You can see the type of any value or expression with `:t`: ->:t foo +> :t foo foo :: Integer +-- Operators, such as `+`, `:` and `$`, are functions. +-- Their type can be inspected by putting the operator in parentheses: + +> :t (:) +(:) :: a -> [a] -> [a] + +-- You can get additional information on any `name` using `:i`: + +> :i (+) +class Num a where + (+) :: a -> a -> a + ... + -- Defined in ‘GHC.Num’ +infixl 6 + + -- You can also run any action of type `IO ()` > sayHello -- cgit v1.2.3 From 410cc03b09870be6da4931725120b44f93b3bcfc Mon Sep 17 00:00:00 2001 From: Robb Shecter Date: Thu, 3 Dec 2015 14:27:24 -0800 Subject: Updating dev environment installation info --- haskell.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 936744a0..34eee748 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -426,7 +426,7 @@ qsort (p:xs) = qsort lesser ++ [p] ++ qsort greater greater = filter (>= p) xs ``` -Haskell is easy to install. Get it [here](http://www.haskell.org/platform/). +There are two popular ways to install Haskell: The traditional [Cabal-based installation](http://www.haskell.org/platform/), and the newer [Stack-based process](https://www.stackage.org/install). You can find a much gentler introduction from the excellent [Learn you a Haskell](http://learnyouahaskell.com/) or -- cgit v1.2.3 From d064763e9599f3ef4b7bccc1ed7d9df3687367ac Mon Sep 17 00:00:00 2001 From: Patrik Jansson Date: Thu, 9 Feb 2017 16:26:11 +0100 Subject: [haskell/en] some minor fixes (#2550) * [haskell/en] some minor fixes * Minor fixes after comments from @vendethiel --- haskell.html.markdown | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 4ce1a839..2b6aa2f7 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -68,7 +68,7 @@ not False -- True ---------------------------------------------------- -- Every element in a list must have the same type. --- These two lists are the same: +-- These two lists are equal: [1, 2, 3, 4, 5] [1..5] @@ -77,11 +77,11 @@ not False -- True -- You can create a step in a range. [0,2..10] -- [0, 2, 4, 6, 8, 10] -[5..1] -- This doesn't work because Haskell defaults to incrementing. +[5..1] -- [] (Haskell defaults to incrementing) [5,4..1] -- [5, 4, 3, 2, 1] -- indexing into a list -[1..10] !! 3 -- 4 +[1..10] !! 3 -- 4 (zero-based indexing) -- You can also have infinite lists in Haskell! [1..] -- a list of all the natural numbers @@ -152,8 +152,8 @@ fib x | otherwise = fib (x - 1) + fib (x - 2) -- Pattern matching is similar. Here we have given three different --- definitions for fib. Haskell will automatically call the first --- function that matches the pattern of the value. +-- equations for fib. Haskell will automatically use the first +-- equation whose left hand side pattern matches the value. fib 1 = 1 fib 2 = 2 fib x = fib (x - 1) + fib (x - 2) @@ -198,11 +198,11 @@ foo 5 -- 15 -- multiplies the result of that by 4, and then returns the final value. foo = (4*) . (10+) --- 4*(10 + 5) = 60 +-- 4*(10+ 5) = 60 foo 5 -- 60 -- fixing precedence --- Haskell has another operator called `$`. This operator applies a function +-- Haskell has an operator called `$`. This operator applies a function -- to a given parameter. In contrast to standard function application, which -- has highest possible priority of 10 and is left-associative, the `$` operator -- has priority of 0 and is right-associative. Such a low priority means that @@ -244,10 +244,10 @@ double x = x * 2 -- 6. Control Flow and If Expressions ---------------------------------------------------- --- if expressions +-- if-expressions haskell = if 1 == 1 then "awesome" else "awful" -- haskell = "awesome" --- if expressions can be on multiple lines too, indentation is important +-- if-expressions can be on multiple lines too, indentation is important haskell = if 1 == 1 then "awesome" else "awful" @@ -295,11 +295,10 @@ data Color = Red | Blue | Green -- Now you can use it in a function: - say :: Color -> String -say Red = "You are Red!" -say Blue = "You are Blue!" -say Green = "You are Green!" +say Red = "You are Red!" +say Blue = "You are Blue!" +say Green = "You are Green!" -- Your data types can have parameters too: @@ -384,8 +383,8 @@ main'' = do -- The type `IO` is an example of a "monad". The way Haskell uses a monad to -- do IO allows it to be a purely functional language. Any function that -- interacts with the outside world (i.e. does IO) gets marked as `IO` in its --- type signature. This lets us reason about what functions are "pure" (don't --- interact with the outside world or modify state) and what functions aren't. +-- type signature. This lets us reason about which functions are "pure" (don't +-- interact with the outside world or modify state) and which functions aren't. -- This is a powerful feature, because it's easy to run pure functions -- concurrently; so, concurrency in Haskell is very easy. -- cgit v1.2.3 From 0a0080a955c11c9b29757d20c74412e6ced67f16 Mon Sep 17 00:00:00 2001 From: ven Date: Thu, 9 Feb 2017 16:27:29 +0100 Subject: #2550 --- haskell.html.markdown | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 2b6aa2f7..ce804415 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -152,7 +152,7 @@ fib x | otherwise = fib (x - 1) + fib (x - 2) -- Pattern matching is similar. Here we have given three different --- equations for fib. Haskell will automatically use the first +-- equations that define fib. Haskell will automatically use the first -- equation whose left hand side pattern matches the value. fib 1 = 1 fib 2 = 2 @@ -198,7 +198,7 @@ foo 5 -- 15 -- multiplies the result of that by 4, and then returns the final value. foo = (4*) . (10+) --- 4*(10+ 5) = 60 +-- 4*(10+5) = 60 foo 5 -- 60 -- fixing precedence -- cgit v1.2.3 From 63a6eb1182205389388e13b680962199ac9b3ffb Mon Sep 17 00:00:00 2001 From: Andy Date: Sat, 1 Apr 2017 22:19:58 +0200 Subject: [haskell] Updating second headline (#2695) * Haskell: Updating second headline * Haskell: Updating second headline (es) * Haskell: Updating second headline (fr) * Haskell: Updating second headline (pl) * Haskell: Updating second headline (pt) * Haskell: Updating second headline (ro) * Haskell: Updating second headline (ru) * Haskell: Updating second headline (cn) --- haskell.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index ce804415..4e254070 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -64,7 +64,7 @@ not False -- True ---------------------------------------------------- --- Lists and Tuples +-- 2. Lists and Tuples ---------------------------------------------------- -- Every element in a list must have the same type. -- cgit v1.2.3 From 21b76a0179735a88a49324ae6ca1f719f0b5ee94 Mon Sep 17 00:00:00 2001 From: Pratik Karki Date: Fri, 25 Aug 2017 13:46:38 +0545 Subject: Add filename(#2832) --- haskell.html.markdown | 1 + 1 file changed, 1 insertion(+) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 4e254070..70ef8fb2 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -1,5 +1,6 @@ --- language: Haskell +filename: learnhaskell.hs contributors: - ["Adit Bhargava", "http://adit.io"] --- -- cgit v1.2.3 From 177db388313bfc4aa538ee4bfa54d5b72a09537a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andre=20Polykanine=20A=2EK=2EA=2E=20Menelion=20Elens=C3=BA?= =?UTF-8?q?l=C3=AB?= Date: Sun, 10 Sep 2017 22:26:33 +0300 Subject: [haskell/en] Added Happy Learn Haskell Tutorial. Fixed #2177 --- haskell.html.markdown | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'haskell.html.markdown') diff --git a/haskell.html.markdown b/haskell.html.markdown index 70ef8fb2..266cf11b 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -444,5 +444,6 @@ qsort (p:xs) = qsort lesser ++ [p] ++ qsort greater There are two popular ways to install Haskell: The traditional [Cabal-based installation](http://www.haskell.org/platform/), and the newer [Stack-based process](https://www.stackage.org/install). You can find a much gentler introduction from the excellent -[Learn you a Haskell](http://learnyouahaskell.com/) or +[Learn you a Haskell](http://learnyouahaskell.com/), +[Happy Learn Haskell Tutorial](http://www.happylearnhaskelltutorial.com/) or [Real World Haskell](http://book.realworldhaskell.org/). -- cgit v1.2.3