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1if not modules then modules = { } end modules ['typo-lan'] = {
2    version   = 1.001,
3    comment   = "companion to typo-lan.mkiv",
4    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
5    copyright = "PRAGMA ADE / ConTeXt Development Team",
6    license   = "see context related readme files"
7}
8
9local type, next = type, next
10
11local currentfont       = font.current
12local setmetatableindex = table.setmetatableindex
13local utfbyte           = utf.byte
14
15local hashes            = fonts.hashes
16local fontdata          = hashes.characters
17local emwidths          = hashes.emwidths
18
19local frequencies       = languages.frequencies or { }
20languages.frequencies   = frequencies
21
22local frequencydata     = { }
23local frequencyfile     = string.formatters["lang-frq-%s.lua"]
24local frequencycache    = { }
25
26setmetatableindex(frequencydata, function(t,language)
27    local fullname = resolvers.findfile(frequencyfile(language))
28    local v = fullname ~= "" and dofile(fullname)
29    if not v or not v.frequencies then
30        v = t.en
31    end
32    t[language] = v
33    return v
34end)
35
36setmetatableindex(frequencycache, function(t,language)
37    local dataset = frequencydata[language]
38    local frequencies = dataset.frequencies
39    if not frequencies then
40        return t.en
41    end
42    local v = { }
43    setmetatableindex(v, function(t,font)
44        local average = emwidths[font] / 2
45        if frequencies then
46            local characters = fontdata[font]
47            local sum, tot = 0, 0
48            for k, v in next, frequencies do
49                local character = characters[k] -- characters[type(k) == "number" and k or utfbyte(k)]
50                tot = tot + v
51                sum = sum + v * (character and character.width or average)
52            end
53            average = sum / tot -- widths
54        end
55        t[font] = average
56        return average
57    end)
58    t[language] = v
59    return v
60end)
61
62function frequencies.getdata(language)
63    return frequencydata[language]
64end
65
66function frequencies.averagecharwidth(language,font)
67    return frequencycache[language or "en"][font or currentfont()]
68end
69
70interfaces.implement {
71    name      = "averagecharwidth",
72    actions   = { frequencies.averagecharwidth, context },
73    arguments = "string"
74}
75