diff options
| -rw-r--r-- | README.md | 2 | ||||
| -rw-r--r-- | ch06/6_a_2.txt | 33 |
2 files changed, 34 insertions, 1 deletions
@@ -105,7 +105,7 @@ of a group is in bold italics. | **_5_a_1_** | yes | 130 | 5. Writing a library: working with JSON data | | 5_a_2 | yes, in 5_a_1 | | | | **_6_a_1_** | yes | 162 | 6. Using typeclasses | -| 6_a_2 | | | | +| 6_a_2 | yes | | | | **_8_a_1_** | | 205 | 8. Efficient file processing, regular expressions, and file name matching | | 8_a_2 | | | | | **_8_b_1_** | | 210 | | diff --git a/ch06/6_a_2.txt b/ch06/6_a_2.txt new file mode 100644 index 0000000..8c410c9 --- /dev/null +++ b/ch06/6_a_2.txt @@ -0,0 +1,33 @@ +-- What is the type of (,)? When you use it in ghci, what does it do? What about +-- (,,)? + +-- (,) is a 2-tuple data constructor + +ghci> :t (,) +(,) :: a -> b -> (a, b) + +ghci> (,) 1 2 +(1,2) + +ghci> t = (,) 1 +ghci> :t t +t :: Num a => b -> (a, b) +ghci> t 2 +(1,2) + +-- (,,) is a 3-tuple data constructor + +ghci> :t (,,) +(,,) :: a -> b -> c -> (a, b, c) + +ghci> (,,) 1 2 3 +(1,2,3) + +ghci> t = (,,) 1 +ghci> :t t +t :: Num a => b -> c -> (a, b, c) +ghci> u = t 2 +ghci> :t u +u :: (Num a, Num b) => c -> (a, b, c) +ghci> u 3 +(1,2,3) |