remy-j-a-moueza/stacky

A postscript inspired language experiment.

Stacky

Stacky was a postscript inspired stack language.

The project had a simple purpose: try to make a programming language and fail fast to learn from it.

Some relative success came along the way. The implementation is not optimized at all. I also changed directions numerous times. I stalled when I attempted to introduce types.

code samples

Comments

% comments start with a percent signe 

Multiline comments are buggy in the last implementation.

%( Multiple 
   line
   comments )%

Literals

• Booleans

true
false

• Strings:

"hello world!\n"

• Raw Strings:

r"\n is not escaped here"

• Integers:

1 2 

• Floats:

1.2 3.14

• Arrays: sequence delimited by parentheses

( 1 2 3 )

• Dictionaries: sequence of pairs delimeted by squared brackets

stacky> [ 1 "hello" 2 "world" ]
[2i: "world", 1i: "hello"]

• Functions: sequence of literals within curly braces

{ 5 + }

Anything else refers to a symbol defined in a global or local dictionary.

Symbols can be escaped so as to not be interpreted by prefixing them by a /. This can be used in conjonction with def to define variables.

/hello "hello" def

Function examples

• A sum

/sum {
    0 swap { + } for-all
} def

• A range function

/range { 
    () 3 swapn { 
        swap push 
    } for 
} def

1 1 10 range sum print-ln

• Test a predicate holds for all the values within an array.

/all { 
    /proc   swap def 
    /array  swap def
    /status true def
    
    array { 
        proc true = not { 
            /status false def 
        } if 
    } for-all
    
    status
} def 

( 1 2 3 ) { 5 < } all

• Test that one element of an array satisfies a given predicate.

/any { 
    /proc   swap def 
    /array  swap def
    
    array { 
        proc true = { 
            true 
            return
        } if 
    } for-all
} def 

( 1 2 3 ) { 5 < } any

• The map function

/map {
    /proc   swap  def
    /source swap  def
    /target  ()   def 

    source { proc target push } for-all

    target
} def

• The filter function

/filter {
    /proc   swap def
    /source swap def 
    /target  ()  def

    source {
        dup proc true =
        { target push } { drop } if-else
    } for-all
    
    target
} def