id,tool_id,filename,language,content
13,2,entropy.c,c,"/* entropy — calculate shannon entropy of input */

#include <math.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
	FILE *fp;
	unsigned long freq[256] = {0};
	unsigned long total = 0;
	int c;
	double entropy = 0.0;

	fp = (argc > 1) ? fopen(argv[1], ""rb"") : stdin;
	if (!fp) {
		perror(argv[1]);
		return 1;
	}

	while ((c = fgetc(fp)) != EOF) {
		freq[c]++;
		total++;
	}

	if (fp != stdin)
		fclose(fp);

	if (total == 0) {
		printf(""0.000000\n"");
		return 0;
	}

	for (int i = 0; i < 256; i++) {
		if (freq[i] == 0)
			continue;
		double p = (double)freq[i] / total;
		entropy -= p * log2(p);
	}

	printf(""%.6f\n"", entropy);
	return 0;
}
"
14,2,entropy.py,py,"#!/usr/bin/env python3
""""""entropy — calculate shannon entropy of input""""""

import math
import sys
from collections import Counter

def entropy(data: bytes) -> float:
    if not data:
        return 0.0
    counts = Counter(data)
    total = len(data)
    return -sum((c / total) * math.log2(c / total) for c in counts.values())

def main():
    if len(sys.argv) > 1:
        with open(sys.argv[1], ""rb"") as f:
            data = f.read()
    else:
        data = sys.stdin.buffer.read()
    print(f""{entropy(data):.6f}"")

if __name__ == ""__main__"":
    main()
"