Add Basics/Types by lbseale · Pull Request #41 · haskellfoundation/HaskellSchool

lbseale · 2021-11-05T15:18:19Z

Add types module

Covering (for now)

Static Type
Type Inference
Bools, Ints, Floats, Chars, Text
Why we don't use String

This is just the start, I plan to add more details

Submitter checklist

My PR is related to Issue English - Basics/Types #38
My PR follows the code style
My PR follows the style guide for my language
I have read and understood the CONTRIBUTING guide

- Merge of types-01 commit 5100108 Author: Luke Seale <19484084+lbseale@users.noreply.github.com> Date: Fri Nov 5 06:42:35 2021 -0700 Add types module Covering - Static Type - Type Inference - Bools, Ints, Floats, Chars, Text - Why we don't use String

Kleidukos · 2021-11-28T17:29:28Z

en/lessons/basics/types.md

+negativeInteger :: Integer
+negativeInteger = -37
+```
+


Any chance you could add a little something about Word? I'm especially interested in promoting it as a type that can't be negative, instead of using Int and hoping for the best. It's also the occasion to evoke the correct by construction paradigm.

Consider mentioning Natural instead of or together with Word?

And the fact that arithmetic underflows are handled differently:

When doing 0 - 1

Since Word is modular, it loops back to 18446744073709551615

In the case of Natural, an arithmetic underflow exception is thrown

Kleidukos · 2021-11-28T17:30:14Z

en/lessons/basics/types.md

+```haskell
+someText :: Text
+someText = "Let's learn Haskell"
+```


Could you add a couple of examples for Text? Especially the functions that do not exist in base for String?

Yes, great idea

soupi · 2021-12-08T11:45:39Z

en/lessons/basics/types.md

+## Static Typing
+
+Haskell is a statically-typed programming language. This means that the type
+of all data must be known before the program is compiled. Some imperative 


Suggested change

of all data must be known before the program is compiled. Some imperative

of all data must be known before the program is executed. Some

soupi · 2021-12-08T11:51:20Z

en/lessons/basics/types.md

+Instead of declaring the type of every single function and variable, Haskell
+can *infer* the type of values based on just a few declarations.
+
+Typically, you just need to specify the type of a function. The types of all


Since this isn't actually required, consider saying something like this instead:

while Haskell does not require type annotations in most cases, it is good practice to annotate the types of top-level definitions. This adds an extra layer of documentation, and safety where the Haskell compiler can verify our intent (as expressed in the type annotation) matches the code.

soupi · 2021-12-08T11:52:52Z

en/lessons/basics/types.md

+## Type Declarations
+
+In Haskell, you declare types on a separate line from where they are used. 
+Even though I said above that you usually only declare types for functions, in


You can avoid this line by saying "top-level definitions"

soupi · 2021-12-08T11:55:46Z

en/lessons/basics/types.md

+Type inference is a killer feature of Haskell, and once you get used to it, you
+won't want to work without it.
+
+## Type Declarations


Consider changing this to "type signatures" or "type annotations", so it won't be confused with declaring new types (using data/newtype/etc)

soupi · 2021-12-08T11:57:12Z

en/lessons/basics/types.md

+```
+
+The fact that `Int`'s size is limited means it is subject to overflows. These 
+occur without warning, so if they are a concern, use `Integer`


Suggested change

occur without warning, so if they are a concern, use `Integer`

occur without warning, so if they are a concern, use `Integer`.

soupi · 2021-12-08T12:01:15Z

en/lessons/basics/types.md

+
+import Data.Text ( Text )
+```
+


Maybe add "we'll explain why this is needed later" or something similar?

soupi · 2021-12-08T12:03:45Z

en/lessons/basics/types.md

+
+`Text` is more convenient, performant and capable than `String`. We want 
+beginners to avoid the mistakes of the past and start off with good 
+practices, so we have chosen to teach `Text`. 


Maybe this would be a good place to mention that text lives in a different package/module, what overloadedstrings does, and how to convert String <-> Text?

Begin Types

e8a5fa1

- Merge of types-01 commit 5100108 Author: Luke Seale <19484084+lbseale@users.noreply.github.com> Date: Fri Nov 5 06:42:35 2021 -0700 Add types module Covering - Static Type - Type Inference - Bools, Ints, Floats, Chars, Text - Why we don't use String

lbseale changed the title ~~Add Basics/TYpes~~ Add Basics/Types Nov 5, 2021

Kleidukos requested changes Nov 28, 2021

View reviewed changes

soupi reviewed Dec 8, 2021

View reviewed changes

	of all data must be known before the program is compiled. Some imperative
	of all data must be known before the program is executed. Some

	occur without warning, so if they are a concern, use `Integer`
	occur without warning, so if they are a concern, use `Integer`.


		import Data.Text ( Text )
		```

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lbseale commented Nov 5, 2021

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