Re: [dev] nscript - a little stack-based scripting language interpretter I wrote

  Wow! pretty fun :)

I encourage you to make the nstest program smarter by removing help
messages, prompts and others and just keep the read-eval-print loop.

About the language I find it quite nice as in syntax. I wrote a similar
virtual machine in 'sal' but it end up being a little messy and close to
raw assembly than fortran.

Here'r my thoughts:

* I would probably prefer '"' quote char for strings.
* Remove 'code' in nstest.c and put it as a testcase t/test
* function to execute commands in shell and get output in stack
* floating point support (append '.' or 'f' to each basic math op +. ,
-. ...)
* Onechar and line input reading
* format string implementation (maybe)
* type check functions (how can I know the type of the last element in
the stack?
* I will probably swap the order of the conditional clauses: (what do
you think about it)
     3 3 == { 'Is equal duppy\n' print } if
   -->
    { 'Is equal duppy\n' print } 3 3 == if

Congratz for the code, it can be cleaned up, but the LOC and use is
impressive. I really enjoy it.

--pancake

On 08/25/10 02:24, Nikhilesh S wrote:
> On Wed, 25 Aug 2010, yy wrote:
>
>> It is difficult to form an opinion about a language if there is no
>> documentation or any examples, and it is difficult to form an opinion
>> about the implementation without understanding the language.
>>
>> What features does it have? How does it look like? How does it compare
>> to other stack-based languages like toka or raven?
>
> It's not really very big actually. I don't think anyone could (or would
> want to) actually /use/ it, so I didn't include much documentation.
>
> But it looks like this -
>
> Comments start with '#' and continue till the end of the line. For now
> there are just 5 types - 'boolean', 'integer', 'string', 'function' and
> 'block'. Strings are delimited by single quotes.
>
> To push the integer 2 onto the stack:-
>
> 2
>
> 'print' will pop and print the last object on the stack
>
> 2 print # prints '2'
>
> '+' pops the last two integers on the stack, and pushes their sum
> (implementation-wise it just pops and adds the last integer into the
> second-last)
>
> 2 3 + print # prints '5'
>
> Preceding a name with '$' will create a variable with that name and pop
> and assign the last thing on the stack to it. Simply a name will push
> the value of the variable with that name onto the stack (if it's not
> executable, we're getting to executables soon).
>
> 3 $var 2 5 var + print # prints '8', 2 is left on stack
>
> Putting code between '{' and '}' will push a block onto the stack, with
> that code in it. This can be used with, for example, the 'repeat'
> function, like this
>
> { 'hi' print } 3 repeat # prints 'hihihi'
>
> You can make your own functions by assigning blocks to variables. When
> you write a name, and it refers to a variable that's executable (a
> block) then it gets executed.
>
> { 3 + print } $print3greater
>
> 5 print3greater # prints '8'
>
> You can push a block-variable onto the stack without executing it by
> prefixing it with an '&'. This can be done for built-in functions too.
>
> 1 2 3 4 &add 3 repeat print # prints '10'
>
> Here's some example factorial code:-
>
> { dup 0 == { 1 + } { 1 rot { dup 1 + } rot 1 - dup $oneless repeat
> &* oneless repeat } ifelse } $fact
>
> 10 fact print # prints 10 factorial, that is '3628800'
>
> '==' pops two objects, and pushes back 'true' if they are equal, else
> 'false'
>
> 'dup' duplicates the last object on the stack
>
> 'ifelse' executes the block at 1 on the stack if boolean at 2 is true,
> else executes the block at 0 (the last object on stack is at 0, the
> second last at 1, and so on).
>
> 'rot' swaps the last two objects on the stack
>
> 'fact' works by pushing 1 to n onto the stack first and then
> multiplying them
> together at the end. For 0 it just gives 1.
>
> There's a clearer version of 'fact' with comments in nstest.c. (it
> doesn't work for '0' input though - I will update the code).
>
Received on Wed Aug 25 2010 - 13:54:37 CEST