7 ms·

A "Why Pure?" section would be useful. The symbolic manipulation part is something I haven't encountered in other mainstream languages (at the level of the lang

by elbear 3y ago

A "Why Pure?" section would be useful. The symbolic manipulation part is something I haven't encountered in other mainstream languages (at the level of the language). It's equivalent to Python's SymPy, right?

elpatokamo 3y ago
There is a section in GitHub, which is where most of the documentation seems to be anyway. This FAQ is linked directly from the website. https://github.com/agraef/pure-lang/wiki/FAQ#why-pure https://github.com/agraef/pure-lang/wiki/FAQ#why-pure
lebean 3y ago
Giving you a reason why would make it unpure. To be a pure language, one should use it solely for the pure pleasure of using it.
- elbear 3y ago
  Funny argument, not necessarily in a bad way. Still, something to entice the reader would be welcome.
sterlind 3y ago
Yes, Pure is a term-rewriting system, similar to SymPy. Transformation rules define patterns to match in expressions, what bindings to capture from the match, and what to transform the matched pattern into. This is also how the XL language seemed to work. The major difference between a term-rewriting system and a general-purpose functional/declarative language is that you don't need to define everything. Expressions will be transformed until they can't anymore, and then they're left alone. So you can e.g. implement symbolic differentiation as a set of rules, and take the derivative of a symbolic expression, because the variables (or even entire functions!) just don't need to be defined. The king of all term-rewriting systems is (imo) Mathematica. It's extraordinarily powerful, capable of matching subtrees and variable arity expressions and it's perfect for doing card tricks with algebraic identities. Unfortunately proprietary. Sadly, term-rewriting languages are languishing. Even Pure is pretty dead.
- bloaf 3y ago
  Its a shame, because there is a lot of really cool stuff you can do when you're able to work with your code in algebraic terms. Just as one simple example: Suppose you have defined some expressions that describe how to read/write data from a database, and you have used them to define a workflow-expression that retrieves a bunch of data, does some math on it, and displays the result. In Mathematica, you can plug that whole workflow-expression into the "Simplify" function and it will potentially eliminate entire database calls if it realizes you've got stuff like "GetData[y]*(GetData[x]-GetData[x])" in your result that will always evaluate to 0. You can even do things like define a high "complexity" of your GetData functions to make the Simplify function look for an algebraic form that will minimize calls to the database, even if it has to make the algebra look uglier.
  - elbear 3y ago
    Wow, this sounds like something with a lot of potential. It also makes me think the book Algebra-Driven Design[1]. That coupled with what you're describing sounds like a powerful combination. [1]: https://reasonablypolymorphic.com/blog/algebra-driven-design/index.html https://reasonablypolymorphic.com/blog/algebra-driven-design...
- hcarvalhoalves 3y ago
  This library bring these capabilities to Clojure: https://github.com/mentat-collective/emmy https://github.com/mentat-collective/emmy It's based on an older library for Scheme, by Sussman.
- jjtheblunt 3y ago
  Mathematica user since 1988: i think it, in retrospect, might be great that it’s proprietary, in that it dampens its likelihood of trend-driven over commitment and resulting irrelevance.
  - JadeNB 3y ago
    > Mathematica user since 1988: i think it, in retrospect, might be great that it’s proprietary, in that it dampens its likelihood of trend-driven over commitment and resulting irrelevance. I think that's not really true. It's not that Mathematica isn't trend-driven, just that it's responsive to trends more or less to the extent that Wolfram (company or person) is, rather than to the extent that the entire developer community is. Depending on how you use it, you may or may not like its embrace of new trends; while I've occasionally been glad it can do $CoolThing, I have also wondered sometimes why my Mathematica install needed to grow from, at some point in the single-digit versions where it was perfectly useful, a few hundred megabytes to now nearly 9 GB.

by elbear 3y ago

elpatokamo 3y ago

There is a section in GitHub, which is where most of the documentation seems to be anyway. This FAQ is linked directly from the website. https://github.com/agraef/pure-lang/wiki/FAQ#why-pure https://github.com/agraef/pure-lang/wiki/FAQ#why-pure

lebean 3y ago

Giving you a reason why would make it unpure. To be a pure language, one should use it solely for the pure pleasure of using it.

elbear 3y ago
Funny argument, not necessarily in a bad way. Still, something to entice the reader would be welcome.

sterlind 3y ago

Yes, Pure is a term-rewriting system, similar to SymPy. Transformation rules define patterns to match in expressions, what bindings to capture from the match, and what to transform the matched pattern into. This is also how the XL language seemed to work. The major difference between a term-rewriting system and a general-purpose functional/declarative language is that you don't need to define everything. Expressions will be transformed until they can't anymore, and then they're left alone. So you can e.g. implement symbolic differentiation as a set of rules, and take the derivative of a symbolic expression, because the variables (or even entire functions!) just don't need to be defined. The king of all term-rewriting systems is (imo) Mathematica. It's extraordinarily powerful, capable of matching subtrees and variable arity expressions and it's perfect for doing card tricks with algebraic identities. Unfortunately proprietary. Sadly, term-rewriting languages are languishing. Even Pure is pretty dead.

bloaf 3y ago
Its a shame, because there is a lot of really cool stuff you can do when you're able to work with your code in algebraic terms. Just as one simple example: Suppose you have defined some expressions that describe how to read/write data from a database, and you have used them to define a workflow-expression that retrieves a bunch of data, does some math on it, and displays the result. In Mathematica, you can plug that whole workflow-expression into the "Simplify" function and it will potentially eliminate entire database calls if it realizes you've got stuff like "GetData[y]*(GetData[x]-GetData[x])" in your result that will always evaluate to 0. You can even do things like define a high "complexity" of your GetData functions to make the Simplify function look for an algebraic form that will minimize calls to the database, even if it has to make the algebra look uglier.
- elbear 3y ago
  Wow, this sounds like something with a lot of potential. It also makes me think the book Algebra-Driven Design[1]. That coupled with what you're describing sounds like a powerful combination. [1]: https://reasonablypolymorphic.com/blog/algebra-driven-design/index.html https://reasonablypolymorphic.com/blog/algebra-driven-design...
hcarvalhoalves 3y ago
This library bring these capabilities to Clojure: https://github.com/mentat-collective/emmy https://github.com/mentat-collective/emmy It's based on an older library for Scheme, by Sussman.
jjtheblunt 3y ago
Mathematica user since 1988: i think it, in retrospect, might be great that it’s proprietary, in that it dampens its likelihood of trend-driven over commitment and resulting irrelevance.
- JadeNB 3y ago
  > Mathematica user since 1988: i think it, in retrospect, might be great that it’s proprietary, in that it dampens its likelihood of trend-driven over commitment and resulting irrelevance. I think that's not really true. It's not that Mathematica isn't trend-driven, just that it's responsive to trends more or less to the extent that Wolfram (company or person) is, rather than to the extent that the entire developer community is. Depending on how you use it, you may or may not like its embrace of new trends; while I've occasionally been glad it can do $CoolThing, I have also wondered sometimes why my Mathematica install needed to grow from, at some point in the single-digit versions where it was perfectly useful, a few hundred megabytes to now nearly 9 GB.