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| author | Adam Bard <github@adambard.com> | 2018-09-08 09:48:48 -0700 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2018-09-08 09:48:48 -0700 |
| commit | e6b01188bf23d747c190b201fa7f0dafec31782c (patch) | |
| tree | 909eebc77b92a360acc16a7e8740a0b9122f8aca | |
| parent | e6c27bb8201e43585f53c3adc8cb8c6acae916fa (diff) | |
| parent | d063ea64694226c9490d5fe6da3b960449c3bfe3 (diff) | |
Merge pull request #3157 from alexgrejuc/master
[haskell/en] tweaked tuple information to demonstrate wildcards and a more useful tuple function
| -rw-r--r-- | haskell.html.markdown | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/haskell.html.markdown b/haskell.html.markdown index 266cf11b..90d47c27 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -124,6 +124,9 @@ last [1..5] -- 5 fst ("haskell", 1) -- "haskell" snd ("haskell", 1) -- 1 +-- pair element accessing does not work on n-tuples (i.e. triple, quadruple, etc) +snd ("snd", "can't touch this", "da na na na") -- error! see function below + ---------------------------------------------------- -- 3. Functions ---------------------------------------------------- @@ -159,8 +162,8 @@ fib 1 = 1 fib 2 = 2 fib x = fib (x - 1) + fib (x - 2) --- Pattern matching on tuples: -foo (x, y) = (x + 1, y + 2) +-- Pattern matching on tuples +sndOfTriple (_, y, _) = y -- use a wild card (_) to bypass naming unused value -- Pattern matching on lists. Here `x` is the first element -- in the list, and `xs` is the rest of the list. We can write @@ -203,11 +206,11 @@ foo = (4*) . (10+) foo 5 -- 60 -- fixing precedence --- 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 +-- 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 --- the expression on its right is applied as the parameter to the function on its left. +-- the expression on its right is applied as a parameter to the function on its left. -- before even (fib 7) -- false @@ -223,7 +226,7 @@ even . fib $ 7 -- false -- 5. Type signatures ---------------------------------------------------- --- Haskell has a very strong type system, and every valid expression has a type. +-- Haskell has a very strong type system, and every valid expression has a type. -- Some basic types: 5 :: Integer |