Entropy: Difference between revisions
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(Update to make the program compile with Nim 1.4: added missing type to parameter.) |
MaiconSoft (talk | contribs) (Added Delphi example) |
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{{out}}
<pre>1.84644</pre>
=={{header|Delphi}}==
{{libheader| StrUtils}}
{{libheader| Math}}
{{Trans|Pascal}}
Just fix Pascal code to run in Delphi.
<lang Delphi>
program Entropytest;
uses
StrUtils,
Math;
type
FArray = array of CARDINAL;
var
strng: string = '1223334444';
// list unique characters in a string
function uniquechars(str: string): string;
var
n: CARDINAL;
begin
Result := '';
for n := 1 to length(str) do
if (PosEx(str[n], str, n) > 0) and (PosEx(str[n], Result, 1) = 0) then
Result := Result + str[n];
end;
// obtain a list of character-frequencies for a string
// given a string containing its unique characters
function frequencies(str, ustr: string): FArray;
var
u, s, p, o: CARDINAL;
begin
SetLength(Result, Length(ustr) + 1);
p := 0;
for u := 1 to length(ustr) do
for s := 1 to length(str) do
begin
o := p;
p := PosEx(ustr[u], str, s);
if (p > o) then
INC(Result[u]);
end;
end;
// Obtain the Shannon entropy of a string
function entropy(s: string): EXTENDED;
var
pf: FArray;
us: string;
i, l: CARDINAL;
begin
us := uniquechars(s);
pf := frequencies(s, us);
l := length(s);
Result := 0.0;
for i := 1 to length(us) do
Result := Result - pf[i] / l * log2(pf[i] / l);
end;
begin
Writeln('Entropy of "', strng, '" is ', entropy(strng): 2: 5, ' bits.');
readln;
end.</lang>
=={{header|EchoLisp}}==
<lang scheme>
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</lang>
=={{header|Elena}}==
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