Run-length encoding: Difference between revisions

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This gives RLE encoding for strings and RLE decoding for strings and arrays, e.g., for [[Conway's_Game_of_Life|Conway's Game of Life]]
This gives RLE encoding for strings and RLE decoding for strings and arrays, e.g., for [[Conway's_Game_of_Life|Conway's Game of Life]]
<syntaxhighlight lang=FutureBasic>
<syntaxhighlight lang=FutureBasic>
⚫
local fn decode( string as CFStringRef ) as CFStringRef
⚫
CFStringRef ch, s, t // character, output string, temporary string
⚫
Short i, rl // index, run-length
⚫
s = @"" // Initialize the output string
⚫
for i = 0 to len( string ) - 1 // Decode input string char by char
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ch = mid( string, i, 1 ) // Read character at index
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if intval( ch ) == 0 // Not a digit
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rl = 1
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else
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rl = intval( mid( string, i ) ) // Read run-length counter
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i += fix( log10( rl ) + 1 ) // Move index past digits
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ch = mid( string, i, 1 ) // Read character after run-length
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end if
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t = fn StringByPaddingToLength( ch, rl, ch, 0 ) // Assemble string of chars
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s = fn StringByAppendingString( s, t ) // Add to output string
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next // character
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end fn = s


Dynamic a(1, 1) as Short // Self-fulfilling array


local fn encode( string as CFStringRef) as CFStringRef
local fn encode( string as CFStringRef) as CFStringRef
CFStringRef ch, s, t
CFStringRef ch, s, t
Short i, rl
Short i, rl
s = @""
s = @"" // Initalize the output string
for i = 0 to len( string ) - 1
for i = 0 to len( string ) - 1 // Encode string char by char
ch = mid( string, i, 1)
ch = mid( string, i, 1) // Read character at index
rl = 1 // Start run-length counter
rl = 1 // Start run-length counter
while fn StringIsEqual( mid( string, i + rl, 1), ch )
while fn StringIsEqual( mid( string, i + rl, 1), ch )
rl ++ // Same char, so increase counter
rl ++ // Same char, so increase counter
wend
wend
if rl == 1 then t = @"" else t = fn StringWithFormat( @"%d", rl ) // Ignore count of 1
if rl == 1 then t = @"" else t = fn StringWithFormat( @"%d", rl ) // Counter as string
t = fn StringWithFormat( @"%d", rl ) // Counter as string
t = fn StringByAppendingString( t, ch ) // Add character
t = fn StringByAppendingString( t, ch ) // Add character
s = fn StringByAppendingString( s, t ) // Add to encoded string
i += rl - 1
s = fn StringByAppendingString( s, t ) // Add to output string
i += rl - 1 // Move counter
next
next
end fn = s
print s
⚫
end fn


⚫
local fn decode( string as CFStringRef )
⚫
CFStringRef ch, s, t // character, ouputstring, temporary string
⚫
Short i, rl // index, run length
⚫
s = @"" // Initalize the output string
⚫
for i = 0 to len( string ) - 1 // Decode input string char by char
⚫
ch = mid( string, i, 1 ) // Read character at index
⚫
if intval( ch ) == 0 // Not a digit
⚫
rl = 1
⚫
else
⚫
rl = intval( mid( string, i ) ) // Read run-length counter
⚫
i += fix( log10( rl ) + 1 ) // Move index past digits
⚫
ch = mid( string, i, 1 ) // Read character after run length
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end if
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t = fn StringByPaddingToLength( ch, rl, ch, 0 ) // Assemble string
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s = fn StringByAppendingString( s, t ) // Add to decoded string
⚫
next // character
print s
end fn




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001
001
111
111




</pre>
</pre>
Retrieved from "https://rosettacode.org/wiki/Run-length_encoding"