[gforth] definition of '+place' in <other.fs>

[Marcos Cruz]

I've realized '+place' is defined in two different files and ways.  'see
+place' shows the actual definition is that of <cross.fs>; the second
definition is in <other.fs>:

: +place ( adr len adr )
        2dup c@ + over c!
        dup c@ char+ + swap move ;

I discovered it doesn't work fine.  In order to find the problem, I
dissected it:

: +place ( ca1 len1 ca2 )
  \ Version defined in Gforth's <other.fs>, buggy.
  \ len3 = length of the final string
  \ ca4 = address after the string at ca2
  2dup c@     ( ca1 len1 ca2 len1 len2 )
  +           ( ca1 len1 ca2 len3 )
  over c!     ( ca1 len1 ca2 )
  \ xxx fixme len2 is still needed, but it has been overriden with len3
  dup c@      ( ca1 len1 ca2 len3 )
  char+ +     ( ca1 len1 ca4  )
  swap move
  ;

The length of the second string has to be saved to calculate the
destination address:

: +place ( ca1 len1 ca2 )
  \ Version defined in Gforth's <other.fs>, fixed.
  \ len3 = length of the final string
  \ ca4 = address after the string at ca2
  2dup c@     ( ca1 len1 ca2 len1 len2 )
  dup >r      ( ca1 len1 ca2 len1 len2 ) ( R: len2 )
  +           ( ca1 len1 ca2 len3 )
  over c!     ( ca1 len1 ca2 )
  r>          ( ca1 len1 ca2 len2 ) ( R: )
  char+ +     ( ca1 len1 ca4  )
  swap move
  ;

The definition in <cross.fs> works fine. I dissected it too:

: +place ( ca1 len1 ca2 )
  \ Version defined in Gforth's <cross.fs>.
  \ len3 = length of the final string
  \ ca4 = address after the string at ca2
  2dup >r >r    ( ca1 len1 ca2 ) ( R: ca2 len1 )
  dup c@        ( ca1 len1 ca2 len2 )
  char+ +       ( ca1 len1 ca4 )
  swap move
  r> r>         ( len1 ca2 ) ( R: )
  dup c@        ( len1 ca2 len2 )
  rot +         ( ca2 len3 )
  swap c!
  ;

At first sight the fixed definition of <other.fs> seems faster, with
less stack operations:

: +place ( ca1 len1 ca2 )
  2dup c@ dup >r  + over c!  r> char+ +  swap move
  ;

-- 
Marcos Cruz
http://programandala.net