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add notes on recursion, loop tradeoffs

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crc 2020-01-14 17:47:33 +00:00
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17
doc/RETRO-Book.md
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@ -2460,6 +2460,15 @@ one of these, use `0;`, `-if;` or `if;`.
:test #100 repeat dup #50 eq? [ 'done! s:put nl ] if; n:dec again ;
test
You can also achieve this via recursion:
:test 0; dup n:put sp n:dec test ;
#100 test
Be careful with recursion as the virtual machine will have a limited
amount of space for the address stack and recursing too many times
can cause a stack overflow.
## Counted Loops
There are two combinators for counted loops. These are `times` and
@ -2478,6 +2487,14 @@ The loop indexes can be accessed outside the loop body:
:squares [ display ] times<with-index> nl ;
#100 squares
## Tradeoffs
The unconditional loop form is more efficient as it's just a
simple jump operation. The `times` counted loops are a little
slower, but can be cleaner and more readable in many cases. The
`times<with-index>` form is significantly slower than the other
two forms.
# Working With Numbers
Numbers in RETRO are signed integers.

17
doc/book/techniques/loops
View file

@ -18,6 +18,15 @@ one of these, use `0;`, `-if;` or `if;`.
:test #100 repeat dup #50 eq? [ 'done! s:put nl ] if; n:dec again ;
test
You can also achieve this via recursion:
:test 0; dup n:put sp n:dec test ;
#100 test
Be careful with recursion as the virtual machine will have a limited
amount of space for the address stack and recursing too many times
can cause a stack overflow.
## Counted Loops
There are two combinators for counted loops. These are `times` and
@ -35,3 +44,11 @@ The loop indexes can be accessed outside the loop body:
:display I n:square n:put sp ;
:squares [ display ] times<with-index> nl ;
#100 squares
## Tradeoffs
The unconditional loop form is more efficient as it's just a
simple jump operation. The `times` counted loops are a little
slower, but can be cleaner and more readable in many cases. The
`times<with-index>` form is significantly slower than the other
two forms.