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Add a 'returns' comment for every line of Forth.

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HorseMD 2014-11-13 23:49:06 +00:00
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forth.html.markdown
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@ -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
@ -116,15 +116,15 @@ 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.
@ -138,22 +138,22 @@ 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
@ -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