PyRe

A stack based programming language

Important: This language is a work in progress

TODO

• Check stack effects during compilation time.
• Implement a dependency chain between procedures.
• Do not include unused procedures in the generated code.
• Add an option to generate a graph showing the flow of the program.
• A way to handle dynamic memory.
• A proper type system.
• A way to bind variables inside a block and automatically removing them at the end of it.
• A proper way to interact with files.

Basic example

There's an example emulating rule110

./pyre.py rule110.pyre && ./rule110

Control flow

if elif else

Definition

if condition do

elif condition do

elif condition do

else

end

if, elif and else are similar to labels. The do operator is the most important here. The do operator pops a value from the stack and either continues with the execution or jumps to an appropriate label.

Incidentally, that means the following code is equivalent to the one above:

condition if do

elif condition do

elif condition do

else

end

Note: Currently the do operator only acts on boolean values. The behaviour is undefined for any other type of value.

Examples

if 3 5 + 8 = do
    "8 is equal to (3 + 5)\n" print
end

  if foo 1 = do
    "foo is equal to 1\n" print
elif foo 2 = do
    "foo is equal to 2\n" print
elif foo 3 = do
    "foo is equal to 3\n" print
end

  if foo 5 < do
    "foo is less than 5\n" print
elif foo 6 > do
    "foo is bigger than 6\n" print
elif foo 6 = do
    "foo is equal to 6\n" print
else
    "foo is 5\n" print
end

While loops

Definition

while condition do

end

Examples

1 !foo                    # Assign 1 to foo
while foo 5 < do          # While foo is less than 5
    foo num2char putchar  # Convert foo to a character and print it
    foo++                 # Increment foo
end
'\n' putchar

A more involved example without any variable-binding:

1 5 while 2dup < do        #    a  b a  b <
    swap dup 48 + putchar  #    b  a a 48 + putchar
    1 +                    #    b  a 1  +
    swap                   # (a+1) b
end drop drop              # Drop <a> and <b> from the stack
'\n' putchar

Procedures

procedure name [input variables] -- [output variables] in


end

The procedure can have as many input and output variables as possible. The net effect on the stack of the procedure needs to be output_variables - input_variables

procedure next_fibonacci_pair a b -- c d in
    b     !c  # assign the value of b to c
    a b + !d  # assign the value of a + b to d
end

Running tests

python tests/tests.py