Re: Average of a [stack]

On 11/07/2024 8:08 am, Buzz McCool wrote:

On 6/7/2024 1:32 PM, LIT wrote:

: AVG  DEPTH 0 SWAP DUP >R 0 DO SWAP + LOOP R> / . ;

 
I coincidentally was doing averaging for the floating point stack when I ran across this posting. Other than adding stack comments, how can I improve this word?
 
$ gforth
( Average all values on the floating point stack )
: FloatStackAvg
fdepth   \ Place the number of floating point values on to the stack

r       \ Move the number of floating point values to the return stack

1        \ Initialize loop counter to 1
begin dup r@ <  \ Duplicate counter, see if < fetched number of floats
while    \ while true
f+       \ Add two values on the floating point stack
1 +      \ Increment counter
repeat   \ Repeat test at begin word
r>       \ Move the number of floating point values to the stack
s>f      \ Convert the number of floating point values to a float
f/       \ Divide sum by number of floating point values to get average
drop ;   \ Remove the leftover loop counter value from the stack
 
\ Place values on floating point stack
0.120000e 0.118025e 0.118925e 0.120050e 0.119000e 0.122000e 0.120175e
0.120150e 0.118925e 0.121775e  ok f:10
 
FloatStackAvg  ok f:1
fe. 119.902500000000E-3  ok
 

Simpler to count down.  I find it easier writing for a common-stack model.

: FloatStackAvg ( rn ... r -- avg )
  fdepth dup >r ( count)
  begin  1- dup while ( not done)
    >r  f+ ( add two floats)  r>
  repeat  drop
  r> s>f f/ ( sum/count)
;