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More rewording, mention ?do.

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HorseMD
2014-11-14 10:51:22 +00:00
parent eb83f36015
commit 13a3c11394
1 changed files with 16 additions and 8 deletions
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forth.html.markdown
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@@ -67,11 +67,10 @@ Forth, but most of what is written here should work elsewhere.
\ ------------------------------ Creating Words -------------------------------- \ ------------------------------ Creating Words --------------------------------
\ Quite often one will want to write their own words. \ The `:` word sets Forth into compile mode until it sees the `;` word.
: square ( n -- n ) dup * ; \ ok : square ( n -- n ) dup * ; \ ok
\ The `:` word sets Forth into compile mode until it sees the `;` word. \ We can view what a word does too:
see square \ dup * ; ok see square \ dup * ; ok
\ -------------------------------- Conditionals -------------------------------- \ -------------------------------- Conditionals --------------------------------
@@ -101,19 +100,22 @@ myloop
\ Hello! \ Hello!
\ Hello! ok \ 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`: \ 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 ( -- ) 12 0 do i . loop ; \ ok
one-to-12 \ 0 1 2 3 4 5 6 7 8 9 10 11 12 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`: \ 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 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 : death ( -- ) begin ." Are we there yet?" 0 until ; \ ok
\ ---------------------------- Variables and Memory ---------------------------- \ ---------------------------- Variables and Memory ----------------------------
@@ -195,9 +197,15 @@ myfloatingvar f@ f. \ 4.4 ok
\ specifically for that: \ specifically for that:
clearstack clearstack
\ Clear the screen:
page
\ Loading Forth files: \ Loading Forth files:
\ s" forthfile.fs" included \ s" forthfile.fs" included
\ You can list every word that's in Forth's dictionary (but it's a huge list!):
\ words
\ Exiting Gforth: \ Exiting Gforth:
\ bye \ bye