Difference between revisions of "FP Laboratory 2"
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== Types == | == Types == | ||
| − | + | *Using the GHCi command <code>:info</code>, learn the type of the following functions (and operators): <code>+, sqrt, succ, max</code> | |
| − | + | *Get the information about the data type of following expressions and evaluate them. it is possible using the command <code>:type</code>. You can switch this option on for all commands by <code>:set +t</code> (removing by <code>:unset +t</code>). | |
<syntaxhighlight lang="Haskell" > | <syntaxhighlight lang="Haskell" > | ||
5 + 8 | 5 + 8 | ||
| Line 18: | Line 18: | ||
floor 3.7 | floor 3.7 | ||
ceiling 3.3 | ceiling 3.3 | ||
| + | mod 10 3 | ||
odd 3 | odd 3 | ||
</syntaxhighlight> | </syntaxhighlight> | ||
| − | + | * At presentations, we have spoken about some basic types: <code> Int, Double, Bool, Char</code>. For each of previous expressions assign them the most appropriate of these basic data types. You can verify your guess by using <code>::</code>. For example, for the first expression, lets assume it is <code>Int</code>. We can cast the result to integer and get following result. | |
<syntaxhighlight lang="Haskell" class="myDark" > | <syntaxhighlight lang="Haskell" class="myDark" > | ||
Prelude> :type (5 + 8) :: Int | Prelude> :type (5 + 8) :: Int | ||
Revision as of 12:33, 12 September 2019
Types
- Using the GHCi command
:info, learn the type of the following functions (and operators):+, sqrt, succ, max - Get the information about the data type of following expressions and evaluate them. it is possible using the command
:type. You can switch this option on for all commands by:set +t(removing by:unset +t).
5 + 8
3 * 5 + 8
2 + 4
sqrt 16
succ 6
succ 7
pred 9
pred 8
sin (pi / 2)
truncate pi
round 3.5
round 3.4
floor 3.7
ceiling 3.3
mod 10 3
odd 3
- At presentations, we have spoken about some basic types:
Int, Double, Bool, Char. For each of previous expressions assign them the most appropriate of these basic data types. You can verify your guess by using::. For example, for the first expression, lets assume it isInt. We can cast the result to integer and get following result.
Prelude> :type (5 + 8) :: Int
(5 + 8) :: Int :: Int
If we try incorrect conversion to Char, we get the following result.
Prelude> :type (5 + 8) :: Char
<interactive>:1:2: error:
* No instance for (Num Char) arising from a use of `+'
* In the expression: (5 + 8) :: Char
For this particular expression, also the type Double works.
Prelude> :type (5 + 8) :: Double
(5 + 8) :: Double :: Double
