4 ms·

Wow, can someone explain this story? Its hard to follow if you are not a forth hacker.

by dimitar 13y ago

davidw 13y ago
I think it has something to do with this: http://globalnerdy.com/wordpress/wp-content/uploads/2007/09/forth_on_the_atari.jpg http://globalnerdy.com/wordpress/wp-content/uploads/2007/09/...
- deleted 13y ago
  [deleted]
nocoment 13y ago
It looks like an introduction to FORTH via Kafka.. There is a nice browser interpreter here: http://forthfreak.net/jsforth80x25.html http://forthfreak.net/jsforth80x25.html you can start with: 1 1 + . (+ adds, . prints and this is clearly reverse polish notation) FORTH is in essence an accumulator CPU like the 68000, except it has an easier abstraction to define new instructions (aka "Words") to act like the + or . above.
- emeraldd 13y ago
  Is that another term for a stack machine? I haven't heard of an accumulator cpu before ...
  - nocoment 13y ago
    A CPU with an accumulator register (default locations that accepts the result for each instruction and is usually one of the operands in each new instruction.) I guess that is a bit less capable than an actual stack machine like FORTH but sort of the starting point of this programming mentality (at least as I think of it.)
Someone 13y ago
The tokens coming in are the tokens from the user's ("Him") input. The outer interpreter is what translates those tokens into actions to perform. The inner interpreter performs those actions. In a Forth, both the inner and the outer interpreter are extremely simple. The story describes them in detail. Outer interpreter: look up token in dictionary/dictionaries. If found, instruct inner interpreter to execute it by giving it the address of the function that the token describes. If not found, try interpreting the word as a number in the current base. If that succeeds, push the number on the stack. If it fails, signal an error and clear some state. Inner interpreter: start reading at the address supplied. Recursively interpret every word read as address of another function until encountering a 'end of function' marker. Leo Brodie's variant of this story doesn't use the terms inner and outer interpreter because it was written before the names were invented, but it may be instructive, anyways: http://www.forth.com/starting-forth/sf1/sf1.html http://www.forth.com/starting-forth/sf1/sf1.html
- raverbashing 13y ago
  So the inner interpreter is a VM of some sort? Outer interpreter looks like exactly that, an interpreter (as opposed to a compiler)
  - Someone 13y ago
    Yes, it has been described as such. A main difference/interesting property of this VM is that end users write programs in Forth by extending the VM's instruction set (= the set of dictionary definitions). While in interpreted mode or at compile time (i.e. when the user types words in the terminal), the instruction lookup is slow, through one or more linked lists. At run time, definitions simply consist of lists of pointers to other functions.

Wow, can someone explain this story? Its hard to follow if you are not a forth hacker.

by dimitar 13y ago

Wow, can someone explain this story? Its hard to follow if you are not a forth hacker.

I think it has something to do with this: http://globalnerdy.com/wordpress/wp-content/uploads/2007/09/forth_on_the_atari.jpg http://globalnerdy.com/wordpress/wp-content/uploads/2007/09/...

deleted 13y ago
[deleted]

nocoment 13y ago

It looks like an introduction to FORTH via Kafka.. There is a nice browser interpreter here: http://forthfreak.net/jsforth80x25.html http://forthfreak.net/jsforth80x25.html you can start with: 1 1 + . (+ adds, . prints and this is clearly reverse polish notation) FORTH is in essence an accumulator CPU like the 68000, except it has an easier abstraction to define new instructions (aka "Words") to act like the + or . above.

emeraldd 13y ago
Is that another term for a stack machine? I haven't heard of an accumulator cpu before ...
- nocoment 13y ago
  A CPU with an accumulator register (default locations that accepts the result for each instruction and is usually one of the operands in each new instruction.) I guess that is a bit less capable than an actual stack machine like FORTH but sort of the starting point of this programming mentality (at least as I think of it.)

Someone 13y ago

The tokens coming in are the tokens from the user's ("Him") input. The outer interpreter is what translates those tokens into actions to perform. The inner interpreter performs those actions. In a Forth, both the inner and the outer interpreter are extremely simple. The story describes them in detail. Outer interpreter: look up token in dictionary/dictionaries. If found, instruct inner interpreter to execute it by giving it the address of the function that the token describes. If not found, try interpreting the word as a number in the current base. If that succeeds, push the number on the stack. If it fails, signal an error and clear some state. Inner interpreter: start reading at the address supplied. Recursively interpret every word read as address of another function until encountering a 'end of function' marker. Leo Brodie's variant of this story doesn't use the terms inner and outer interpreter because it was written before the names were invented, but it may be instructive, anyways: http://www.forth.com/starting-forth/sf1/sf1.html http://www.forth.com/starting-forth/sf1/sf1.html

raverbashing 13y ago
So the inner interpreter is a VM of some sort? Outer interpreter looks like exactly that, an interpreter (as opposed to a compiler)
- Someone 13y ago
  Yes, it has been described as such. A main difference/interesting property of this VM is that end users write programs in Forth by extending the VM's instruction set (= the set of dictionary definitions). While in interpreted mode or at compile time (i.e. when the user types words in the terminal), the instruction lookup is slow, through one or more linked lists. At run time, definitions simply consist of lists of pointers to other functions.