[Edu-sig] the string type (was: making types matter (notes for beginners))

[Wes Turner]

On Tuesday, January 29, 2019, kirby urner <kirby.urner at gmail.com> wrote:

>
> Thanks Wes, especially for the URLs relating type theory to "HoTT" by way
> category theory.
>
> My friend and co-podcaster Alex, a math-physics-philo guy, has been
> pushing me to bone up in that area [1].  Those links really helped.
>

https://github.com/ejgallego/jscoq#homotopy-type-theory

"[…] JsCoq/JsHoTT Interactive Online System!"
https://x80.org/rhino-hott/


>
> I'm squeezing some of this in while reading the OSCON 2019 proposals, a
> big job, but I always learn a lot by so doing. [2]
>
> When it comes to Beginner Python and types, people have a strong grasp of
> number types coming in, especially ints, but think they know more about the
> string type than they really do, thanks to the whole coding/decoding
> business.
>

ints and types ... floordiv and div

https://github.com/python/typeshed/blob/master/stdlib/2and3/operator.pyi

> def truediv(a: Any, b: Any) -> Any: ...
> def __truediv__(a: Any, b: Any) -> Any: ...
> if sys.version_info < (3, ):
>    def div(a: Any, b: Any) -> Any: ...
>    def __div__(a: Any, b: Any) -> Any: ...

def div(x: int, y: int) -> Union[float, int]: ...

https://docs.python.org/3/library/operator.html#operator.floordiv
>> 7 // 2

https://docs.python.org/3/library/operator.html#operator.truediv
>> 7 / 2

>> assert sys.version_info.major < 3
>> from __future__ import division
>> 7 / 2

And then there are fractions, and decimals, and arbitrary-precision floats
https://github.com/python/typeshed/blob/master/stdlib/2and3/fractions.pyi


> i.e. strings are always "encrypted" (encoded) a specific way, even if only
> as plain ASCII text.  K-16 doesn't do a lot to introduce Unicode, even
> though it's fundamental.  I'd teach Unicode in language arts, along with
> fonts and old fashioned printing and book binding.
>

Is there a good resource for Unicode with something like the output from
`hexdump -C`?

With Python 3, Unicode emoji just work! :sandwich:


>
> What I find works well with kids and adults alike is a lot of emphasis on
> Emoji, which are now a part of Unicode after all.  They're colorful and
> ubiquitous in modern life.
>
> There's something satisfying about being able to have
>
> ["😉", "🐋", "🚂"]
>
> as a Python list.
>
> We can also use non-keyboard characters in identifiers, though emoji won't
> work (there's no making your emojis callable in other words).
>
> *** testing 1-2-3... how did that list come through in the Mailman
> archives? Displayed as Emoji, not as missing glyphs?  I see Wes already
> used a yellow hand pointing down, so I'm confidant the glyphs should be
> there ***
>
> Contemporary IDEs and web browsers are up to showing emoji.
>

> When you think about Unicode as a database with records (fields as
> attributes) you realize that the string type alone is a huge door opener.
> It's also about number bases and HTML entities.  Lots to know.
>

Strings and Unicode ....

https://en.wikipedia.org/wiki/Executable_space_protection
- What's executable code and what's </data>? Strings are often both, so we
must consider where they'll be output; and we cannot trust user-supplied
input to not contain executable code.

https://en.wikipedia.org/wiki/String_literal#Escape_sequences

https://en.wikipedia.org/wiki/Control_character

https://en.wikipedia.org/wiki/Escape_sequence

https://en.wikipedia.org/wiki/Cross-site_scripting#Preventive_measures

https://en.wikipedia.org/wiki/Cross-site_scripting#Related_vulnerabilities



import string
print(dir(string))
print(string.punctuation)

### https://en.wikipedia.org/wiki/Code_injection#Examples ##

import cgi, http
cgi.escape('''<a href="javascript:alert('hello')">here</a>''')


#
https://docs.python.org/3/library/urllib.parse.html#urllib.parse.quote_plus
import urllib
# urllib.parse.quote_plus
# urllib.parse.unquote


# https://bleach.readthedocs.io/en/latest/
import bleach
bleach.clean("...")
bleach.urlify("...")


https://en.wikipedia.org/wiki/ANSI_escape_code#Escape_sequences
https://en.wikipedia.org/wiki/ANSI_escape_code#Colors
https://github.com/urwid/urwid/blob/master/urwid/escape.py

https://docs.python.org/3/library/shlex.html#shlex.quote

... There are a bunch of packages to add colors to text with Python. You
can also just add raw escape *start* and end* character sequences to
strings and print them out.


>
> About half of my students are middle schoolers [3], the other half are
> adults [4].
>
> The Emoji (Unicode) stuff works at all levels.
>
> I notice the Rust docs are into it.
>
> Show your language is Unicode savvy that way, good PR.
>
> Kirby Urner
> 4dsolutions.net
> cascadia.or.pdx
>
> [1]
> It's something of a joke how everyone starts a Monad tutorial the same
> way, by decrying the dearth of coherent Monad tutorials, hah hah.
>
> The emphasis on composing functions in category theory takes me to this
> decorator class, my Monad in progress:
>
> https://repl.it/@kurner/MakingMonads
>
> https://youtu.be/caSOTjr1z18  (functional programmer speaking to his
> community)
> https://youtu.be/SknxggwRPzU  (Dutch prof with several relevant
> interviews on computerphile channel)
> https://youtu.be/IOiZatlZtGU  (good overview of how logic and CS come
> together over time, focus on lambda stuff).
>

functools, toolz.functoolz, fn.py:

https://docs.python.org/3/library/functools.html#functools.partial
https://docs.python.org/3/library/functools.html#functools.wraps (copies
__doc__ strings over)

https://toolz.readthedocs.io/en/latest/curry.html
https://toolz.readthedocs.io/en/latest/_modules/toolz/functoolz.html

https://github.com/kachayev/fn.py
- #scala-style-lambdas-definition
-
https://github.com/kachayev/fn.py/blob/master/README.rst#high-level-operations-with-functions

> The fn.py fn.monad.optionable decorator — @optionable — makes functional
composition with chaining easy, too:
https://github.com/kachayev/fn.py/blob/master/README.rst#functional-style-for-error-handling


>
> FYI, I've used "λ-calculus" (Church, Turing et al) to loosely brand an
> alternative track through high school, that could in theory count with
> future employers and colleges as much as today's prevelant "Δ-calculus"
> (Newton-Leibniz).
>
> Here's how I use λ-calc in contrast with Δ-calc (against a STEM backdrop
> -- I've since done more to map out PATH).
> https://youtu.be/eTDH7m4vEiM
>
> I'm simply sharing a vision (heuristic, gestalt), akin to science fiction,
> not proposing legislation nor composing any "thou shalt" edict -- so no
> need to get too political about it I'm hoping.  Food for thought.
>
> [2] a Medium story (be me) that gives a big picture broad brush stroke
> history leading up to the resurrection of O'Caml, the language:
> https://medium.com/@kirbyurner/stories-from-cyberia-fc857867e147
>
> [3]  middle school: next Coding with Kids gig starts tomorrow:
> https://youtu.be/6qlj_AZqpto (a look at Codesters)
>
> [4]  adults: next SAISOFT gig starts in February:
> https://github.com/4dsolutions/SAISOFT
> (lots of Jupyter Notebooks; we also use Spyder and vs code, both with
> Anaconda)
>
>
>
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