Burrows–Wheeler transform: Difference between revisions
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BWT: procedure expose ?.; parse arg y,,$ /*obtain the input; nullify $ string. */ |
BWT: procedure expose ?.; parse arg y,,$ /*obtain the input; nullify $ string. */ |
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?.1= 'fd'x; ?.2= "fc"x /*assign the STX and ETX strings. */ |
?.1= 'fd'x; ?.2= "fc"x /*assign the STX and ETX strings. */ |
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do i=1 for 2 |
do i=1 for 2 /* [↓] check for invalid input string.*/ |
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_= verify(y, ?.i, 'M'); if _==0 then iterate; er= '***error*** BWT: ' |
_= verify(y, ?.i, 'M'); if _==0 then iterate; er= '***error*** BWT: ' |
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say er "invalid input: " y |
say er "invalid input: " y |
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say er 'The input string contains an invalid character at position' _"."; exit |
say er 'The input string contains an invalid character at position' _"."; exit _ |
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end /*i*/ /* [↑] if error, perform a hard exit.*/ |
end /*i*/ /* [↑] if error, perform a hard exit.*/ |
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y= ?.1 || y || ?.2 |
y= ?.1 || y || ?.2; L= length(y) /*get the input & add a fence; gel len.*/ |
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@.1= y; m= L - 1 /*define the first element of the table*/ |
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do j=2 for m; _= j-1 /*now, define the rest of the elements.*/ |
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do j=2 for m; _= j-1 /*now, define the rest of the elements.*/ |
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@.j= right(@._,1)left(@._,m) /*construct a table from the Y input.*/ |
@.j= right(@._,1)left(@._,m) /*construct a table from the Y input.*/ |
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end /*j*/ /* [↑] each element: left & right part*/ |
end /*j*/ /* [↑] each element: left & right part*/ |
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call cSort L /*invoke lexicographical sort for array*/ |
call cSort L /*invoke lexicographical sort for array*/ |
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do k=1 for L /* [↓] construct the answer from array*/ |
do k=1 for L /* [↓] construct the answer from array*/ |
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$=$ || right(@.k, 1) |
$= $ || right(@.k, 1) /*build the answer from each of ··· */ |
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end /*k*/ /* ··· the array's right─most character*/ |
end /*k*/ /* ··· the array's right─most character*/ |
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return $ /*return the constructed answer. */ |
return $ /*return the constructed answer. */ |
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