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| -rw-r--r-- | forth.html.markdown | 48 |
1 files changed, 24 insertions, 24 deletions
diff --git a/forth.html.markdown b/forth.html.markdown index c60b8d67..5ffdfbfc 100644 --- a/forth.html.markdown +++ b/forth.html.markdown @@ -50,7 +50,7 @@ Forth, but most of what is written here should work elsewhere. 3 dup - \ duplicate the top item (1st now equals 2nd): 3 - 3 2 5 swap / \ swap the top with the second element: 5 / 2 -6 4 5 rot .s \ rotate the top 3 elements: 4 5 6 ok +6 4 5 rot .s \ rotate the top 3 elements: 4 5 6 4 0 drop 2 / \ remove the top item (dont print to screen): 4 / 2 \ ---------------------- More Advanced Stack Manipulation ---------------------- @@ -103,9 +103,9 @@ myloop \ Hello! \ Hello! ok -\ `do` expects two numbers on the stack: the end number and the index number: +\ `do` expects two numbers on the stack: the end number and the index number. -\ Get the value of the index as we loop with `i`: +\ We can get the value of the index as we loop with `i`: : one-to-12 ( -- ) 12 0 do i . loop ; \ ok one-to-12 \ 0 1 2 3 4 5 6 7 8 9 10 11 12 ok : squares ( -- ) 10 0 do i DUP * . loop ; \ ok @@ -116,49 +116,49 @@ squares \ 0 1 4 9 16 25 36 49 64 81 ok threes \ 0 3 6 9 12 ok \ Finally, while loops with `begin` <stuff to do> <flag> `unil`: -: death ( -- ) begin ." Are we there yet?" 0 until ; +: death ( -- ) begin ." Are we there yet?" 0 until ; \ ok \ ---------------------------- Variables and Memory ---------------------------- \ Use `variable` to declare `age` to be a variable. -variable age +variable age \ ok \ Then we write 21 to age with the word `!`. -21 age ! +21 age ! \ ok \ Finally we can print our variable using the "read" word `@`, which adds the \ value to the stack, or use `?` that reads and prints it in one go. -age @ . \ 12 ok -age ? \ 12 ok +age @ . \ 12 ok +age ? \ 12 ok \ Constants are quite simiar, except we don't bother with memory addresses: -100 constant WATER-BOILING-POINT \ ok -WATER-BOILING-POINT . \ 100 ok +100 constant WATER-BOILING-POINT \ ok +WATER-BOILING-POINT . \ 100 ok \ ----------------------------------- Arrays ----------------------------------- \ Set up an array of length 3: -variable mynumbers 2 cells allot +variable mynumbers 2 cells allot \ ok \ Initialize all the values to 0 -mynumbers 3 cells erase +mynumbers 3 cells erase \ ok \ (alternatively we could do `0 fill` instead of `erase`, but as we're setting \ them to 0 we just use `erase`). \ or we can just skip all the above and initialize with specific values: -create mynumbers 64 , 9001 , 1337 , \ the last `,` is important! +create mynumbers 64 , 9001 , 1337 , \ ok (the last `,` is important!) \ ...which is equivalent to: \ [64, 9001, 1337] -64 mynumbers 0 cells + ! -9001 mynumbers 1 cells + ! -1337 mynumbers 2 cells + ! +64 mynumbers 0 cells + ! \ ok +9001 mynumbers 1 cells + ! \ ok +1337 mynumbers 2 cells + ! \ ok \ Reading values at certain array indexes: -0 cells mynumbers + ? \ 64 ok -1 cells mynumbers + ? \ 9001 ok -2 cells mynumbers + ? \ 1337 ok +0 cells mynumbers + ? \ 64 ok +1 cells mynumbers + ? \ 9001 ok +2 cells mynumbers + ? \ 1337 ok \ Of course, you'll probably want to define your own words to manipulate arrays: : ?mynumbers ( n -- n ) cells mynumbers + ; \ ok @@ -172,10 +172,10 @@ create mynumbers 64 , 9001 , 1337 , \ the last `,` is important! \ We've already seen one use of it: `i`, which duplicates the top of the return \ stack. `i` is equivalent to `r@`. -: myloop ( -- ) 5 0 do r@ . loop ; +: myloop ( -- ) 5 0 do r@ . loop ; \ ok \ As well as reading, we can add to the return stack and remove from it: -5 6 4 >r swap r> .s \ 6 5 4 +5 6 4 >r swap r> .s \ 6 5 4 ok \ NOTE: Because Forth uses the return stack for word pointers, it's essential \ that you set the return stack back to how it was at the end of your @@ -188,9 +188,9 @@ create mynumbers 64 , 9001 , 1337 , \ the last `,` is important! 8.3e 0.8e f+ f. \ 9.1 ok \ Usually we simply prepend words with 'f' when dealing with floats: -variable myfloatingvar \ ok -4.4e myfloatingvar f! \ ok -myfloatingvar f@ f. \ 4.4 ok +variable myfloatingvar \ ok +4.4e myfloatingvar f! \ ok +myfloatingvar f@ f. \ 4.4 ok \ --------------------------------- Final Notes -------------------------------- |