Sats Cats Dats Hats

[Chad Zawistowski]

Hi ATS users!

I'm curious about the naming convention of ATS source files, and I haven't been able to find a completely clear answer (although this page was very helpful).

As far as I can tell, there are four different extensions and they are used thusly:

• Sats -- S for source?
• The primary functional interfaces in ATS are defined in [lib].sats in the SATS directory, where [lib] is our library of interest. The [lib].sats file will reference a .cats file in the CATS directory, which is essentially a C wrapper for the C library functions.
• Cats -- C for the C language?
• The [lib].cats file accomplishes two things: it annotates existing functions and definitions in the C library that are intended to be included in the ATS interface, and more importantly, it often defines C wrappers that more directly reflect the function signature in ATS. The [lib].cats file is a C file, and should include the relevant C library wrappers. Often this is just one C include file:
• Dats -- D for dynamic or definition?
  
• The [lib].dats file in the DATS directory, if it exists, should implement functions that are implemented in ATS but not in the C library (or functions that are implemented in ATS and are preferred over the implementation in C, or dynamic wrappers around the C library functions).
• Hats -- H for header files?
• There can also be a HATS directory containing various .hats files, which is similar to DATS but does not have the one-to-one correspondence that a .dats file would have with a .sats file; this is used for alternative implementations of functions, or in the case of C libraries, possibly alternative implementations of a similar C library (and in this case, each .hats file would likely depend on a particular .cats file as well).

What is the purpose of separating all of these intentions into separate files, and what is the real meaning of the [SCDH] letters?

[Shea Levy]

Hi Chad,

S is for statics. These files are staloaded, and contain type definitions and function declarations, but not implementations.

D is for dynamics. These files are dynloaded, and additionally can be staloaded if they contain declarations that don't exist in a separate statics file. They can contain anything in the sats files, and also implementations.

C is for the c programming language, as you described.

H is for header. These files are #included, and contain code or macro definitions that should be literally copied into other files, like C headers.

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[Chad Zawistowski]

Thanks, Shea!

[Hongwei Xi]

A few more points:

SATS files are just special DATS files. Basically, in DATS, if you declare a function/value,

you need to use 'extern'; you don't in SATS. One does not really need SATS files at all when
programming in ATS.

SATS and DATS are recognized by patscc/patsopt, but CATS and HATS are not.

To view this discussion on the web visit https://groups.google.com/d/msgid/ats-lang-users/56156B21-C609-4749-8A8E-40D836759018%40shealevy.com.

[Chad Zawistowski]

SATS and DATS are recognized by patscc/patsopt, but CATS and HATS are not.

 

In that case, all .cats files might as well be .c, and all .hats files might as well be .h. Is that correct? It seems odd to use a different extension.

[gmhwxi]

CATS could be .js if you do ATS+JS co-programming.

HATS is very different. It is much more general than .h in C.

ATS has a powerful template system that allows you to reassemble code.
In many cases, HATS is just DATS with certain parts missing; the missing
parts are supposed to be found in the surrounding context.

Okay, I don't want to cause too much confusion for the moment.
The ATS story is a very interesting one. It should be most interesting if you
get to know more about ATS :)

[gmhwxi]

A good use of HATS can be found in Chapter 12 (currently) of the following book:

http://ats-lang.sourceforge.net/DOCUMENT/ATS2TUTORIAL/HTML/HTMLTOC/book1.html