OpenEuphoria

Re: can_add() and linear()

• Posted by CChris <christian.cuvier at ag?iculture.g?uv.fr> May 21, 2008
• 652 views

CChris wrote:
> 
> CChris wrote:
> > 
> > I'd suggest two additions to sequence.e, which I hope will appear pretty
> > natural:
> > 
> > }}}
<eucode>
> > global function can_add(object a,object b)
> > -- Determines whether a+b would crash the interpreter.
> > -- Returns 1 if addition possible, else 0.
> >     if atom(a) or atom(b) then
> >         return 1
> >     end if
> >     if length(a)!=length(b) then
> >         return 0
> >     end if
> >     for i=1 to length(a) do
> >         if not can_add(a[i],b[i]) then
> >             return 0
> >         end if
> >     end for
> >     return 1
> > end function
> > 
> > global funtion linear(object start,object increment,integer count)
> > -- Returns 0 on failure, or a sequence of count objects.
> > -- The first one is start, and the whole sequence is a linear progrssion
> > using increment.
> >     sequence result
> > 
> >     if count<0 or not can_add(start,increment) then
> >         return 0
> >     end if
> >     result=repeat(start,count)
> >     for i=2 to count do
> >         start+=increment
> >         result[i]=start
> >     end for
> >     return result
> > end function
> > </eucode>
{{{

> > 
> > The latter might go to math.e just as well, but for its dependency on
> > can_add().
> > 
> > CChris
> 
> More suggestions: 
> 
> global function project(sequence vectors,sequence coords) -- currently in
> sets.e
> -- vectors is a rectangular matrix
> -- coords is a list of coordinate lists
> -- returns a sequence the length of vectors. Each element is a sequence,
> -- the length of coords, of sequences. Each inner sequence is made of the 
> -- coordinates of the vector for the given coord list.
> sequence result,current_vector,coord_set,result_item,projection
> integer current_index
> 
> result=vectors
> for i=1 to length(vectors) do
>     result_item=coords
>     current_vector=vectors[i] 
>     for j=1 to length(coords) do
>         coord_set=coords[j]
>         projection=coord_set
>         for k=1 to length(coords_set) do
>             current_index=coords[k]
>             if current_index<1 or current_index>length(current_vector) then
>                 crash("Invalid coordinate %d in set %d for vector
>                 #%d",{coords[k],j,i})
>             end if
>             projection[k]=current_vector[current_index]
>         end for
>         result_item[j]=projection
>     end for
>     result[i]=result_item
> end for
> return result
> end function
> </eucode>
{{{

> 
> fetch() and store() are useful too - they deal with variable length indexing
> of sequences. The implementation is close to J. Babor's:
> }}}
<eucode>
> global function fetch(sequence s,sequence indexes)
>     for i=1 to length(indexes)-1 do
>         s=s[indexes[i]]
>     end for
>     return s[indexes[$]] 
> end function
> 
> function store-(sequence s,sequence indexes,integer index,object x)
> integer n
> 
> n=indexes[index]
> if index=length(indexes) then
>     s[n]=x
> else
>     s[n]=store_(s[n],indexes,index+1,x)
> end if
> return s
> end function
> 
> global function store(sequence s,sequence indexes,object x)
> return store_(s,indexes,1,x)
> end function
> </eucode>
{{{

> 
> For the sake of simplicity, I didn't consider using slices. A complete version
> is to be found in <a
> href="http://oedoc.free.fr/Fichiers/ESL/seqops.zip,">http://oedoc.free.fr/Fichiers/ESL/seqops.zip,</a>
> which agrees with the OpenEu extended index specification.
> 
> CChris

There hasn't been a single comment regarding this post for the past 8 days. May
I assume that I can go ahead with the additions/moves?

CChris