Applicative Syntax == Concatenative Syntax

Christopher Diggins — 2007-01-16 16:49:34

Consider if we were to define our stack-based (concatenative)

functions as quotations such as:



  define Add { [+] }



We can define the open paranthesis, close paranthesis, and comma as follows:



  define ( { }

  define , { curry }

  define ) { curry eval }



This allows us to write:



  Add(2, 3)



Which leaves the value 5 on the stack just as we would like to see.



I've implemented this in the most recent version of Cat (which I have

posted at http://www.cat-language.com/cat.zip , but haven't officially

announced yet).



-- 

http://www.cdiggins.com

Robbert van Dalen — 2007-01-16 19:41:46

That's really very interesting and inventive - I like it a lot!



but I wouldn't trust such expressions with the correct counting of  

parenthesis, i.e:



Add(2,Add(3,4)))



... oops, 1 closing parenthesis to many...



But I'm sure the curry function can be extended somehow (or that '('  

could be redefined to do something more intelligent) to catch such  

errors.



 On Jan 16, 2007, at 5:49 PM, Christopher Diggins wrote:



> Consider if we were to define our stack-based (concatenative)

> functions as quotations such as:

>

> define Add { [+] }

>

> We can define the open paranthesis, close paranthesis, and comma as  

> follows:

>

> define ( { }

> define , { curry }

> define ) { curry eval }

>

> This allows us to write:

>

> Add(2, 3)

>

> Which leaves the value 5 on the stack just as we would like to see.

>

> I've implemented this in the most recent version of Cat (which I have

> posted at http://www.cat-language.com/cat.zip , but haven't officially

> announced yet).

>

> -- 

> http://www.cdiggins.com

>

> 

William Tanksley, Jr — 2007-01-19 16:59:08

Christopher Diggins <cdiggins@...> wrote:

 > We can define the open paranthesis, close paranthesis, and comma as follows:

>   define ( { }

>   define , { curry }

>   define ) { curry eval }

> This allows us to write:

>   Add(2, 3)

> Which leaves the value 5 on the stack just as we would like to see.



 
Clever and sneaky! I like it.



Of course, I should note that it's missing the main attraction of

applicative languages -- the ability to name parameters. But anyhow,

it's at least a great way to provide a bridge to a traditionally

applicative API, perhaps one that has more parameters being passed to

functions than it really should :-).



And that's _practical_.



-Billy