dice_test_nim.nim

import strutils, tables, parseopt2, system, algorithm, future

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proc dice_coefficient(a:string, b:string): float =

    if len(a) == 0 or len(b) == 0: return 0.0
    # quick case for true duplicates
    if a == b: return 1.0
    # if a != b, and a or b are single chars, then they can't possibly match
    if len(a) == 1 or len(b) == 1: return 0.0

    var
        a_bigram_list = lc[a[i..<i+2] | (i <- 0..<len(a)-1), string]
        b_bigram_list = lc[b[i..<i+2] | (i <- 0..<len(b)-1), string]
        lena = len(a_bigram_list)
        lenb = len(b_bigram_list)
        matches = 0
        i = 0
        j = 0

    sort(a_bigram_list, system.cmp)
    sort(b_bigram_list, system.cmp)
        
    while i < lena and j < lenb:
        if a_bigram_list[i] == b_bigram_list[j]:
            matches += 2
            i += 1
            j += 1
        elif a_bigram_list[i] < b_bigram_list[j]:
            i += 1
        else:
            j += 1
    
    return matches/(lena + lenb)

echo dice_coefficient(args["a"],args["b"])