diff options
| -rw-r--r-- | forth.html.markdown | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/forth.html.markdown b/forth.html.markdown index 46b912b4..b8b751d9 100644 --- a/forth.html.markdown +++ b/forth.html.markdown @@ -67,11 +67,10 @@ Forth, but most of what is written here should work elsewhere. \ ------------------------------ Creating Words -------------------------------- -\ Quite often one will want to write their own words. -: square ( n -- n ) dup * ; \ ok - \ The `:` word sets Forth into compile mode until it sees the `;` word. +: square ( n -- n ) dup * ; \ ok +\ We can view what a word does too: see square \ dup * ; ok \ -------------------------------- Conditionals -------------------------------- @@ -101,19 +100,22 @@ 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 start number. \ 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 ( n -- ) 0 do i dup * . loop ; \ ok -10 squares \ 0 1 4 9 16 25 36 49 64 81 ok + +\ `?do` works similarly, except it will skip the loop if the end and start +\ numbers are equal. +: squares ( n -- ) 0 ?do i dup * . loop ; \ ok +10 squares \ 0 1 4 9 16 25 36 49 64 81 ok \ Change the "step" with `+loop`: -: threes ( n n -- ) do i . 3 +loop ; \ ok +: threes ( n n -- ) ?do i . 3 +loop ; \ ok 15 0 threes \ 0 3 6 9 12 ok -\ Finally, while loops with `begin` <stuff to do> <flag> `unil`: +\ Indefinite loops with `begin` <stuff to do> <flag> `unil`: : death ( -- ) begin ." Are we there yet?" 0 until ; \ ok \ ---------------------------- Variables and Memory ---------------------------- @@ -195,9 +197,15 @@ myfloatingvar f@ f. \ 4.4 ok \ specifically for that: clearstack +\ Clear the screen: +page + \ Loading Forth files: \ s" forthfile.fs" included +\ You can list every word that's in Forth's dictionary (but it's a huge list!): +\ words + \ Exiting Gforth: \ bye |