Run-length encoding: Difference between revisions
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) Rle_Compressed
</syntaxhighlight>
=={{header|SparForte}}==
As a structured script.
<syntaxhighlight lang="ada">#!/usr/local/bin/spar
pragma is
annotate( summary, "rle" );
annotate( description, "Given a string containing uppercase characters (A-Z)," );
annotate( description, "compress repeated 'runs' of the same character by" );
annotate( description, "storing the length of that run, and provide a function to" );
annotate( description, "reverse the compression. The output can be anything, as" );
annotate( description, "long as you can recreate the input with it." );
annotate( description, "" );
annotate( description, "Example:" );
annotate( description, "Input: WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW" );
annotate( description, "Output: 12W1B12W3B24W1B14W" );
annotate( see_also, "http://rosettacode.org/wiki/Run-length_encoding" );
annotate( author, "Ken O. Burtch" );
license( unrestricted );
restriction( no_external_commands );
end pragma;
procedure rle is
function to_rle( s : string ) return string is
begin
if strings.length( s ) = 0 then
return "";
end if;
declare
result : string;
code : character;
prefix : string;
first : natural := 1;
index : natural := 1;
begin
while index <= strings.length( s ) loop
first := index;
index := @+1;
code := strings.element( s, positive(first) );
while index <= strings.length( s ) loop
exit when code /= strings.element( s, positive(index) );
index := @+1;
exit when index-first = 99;
end loop;
prefix := strings.trim( strings.image( index - first ), trim_end.left );
result := @ & prefix & code;
end loop;
return result;
end;
end to_rle;
function from_rle( s : string ) return string is
begin
if strings.length( s ) = 0 then
return "";
end if;
declare
result : string;
index : positive := 1;
prefix : string;
code : character;
begin
loop
prefix := "" & strings.element( s, index );
index := @+1;
if strings.is_digit( strings.element( s, index ) ) then
prefix := @ & strings.element( s, index );
index := @+1;
end if;
code := strings.element( s, index );
index := @+1;
result := @ & ( numerics.value( prefix ) * code );
exit when natural(index) > strings.length( s );
end loop;
return result;
end;
end from_rle;
begin
? to_rle( "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW" );
? from_rle( "12W1B12W3B24W1B14W");
end rle;</syntaxhighlight>
* RLE decoding
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