I have recently been learning and enjoying the Vala programming language. I am writing a lightweight markdown-to-PDF converter and wanted to be able to automatically number list items in Roman numerals. Here, in case anyone wants it, is Knuth’s algorithm for producing the Roman numeral for a number. I converted this to Vala from the original WEB source, part of TeX, as quoted by Hans Wennborg. Enjoy!
string roman(uint num)
{
// Knuth's algorithm for Roman numerals, from TeX. Quoted by
// Hans Wennborg at https://www.hanshq.net/roman-numerals.html.
// Converted to Vala by Chris White (github.com/cxw42). CC-BY 4.0 Intl.
var sb = new StringBuilder();
string control = "m2d5c2l5x2v5i";
int j, k; // mysterious indices into `control`
uint u, v; // mysterious numbers
j = 0;
v = 1000;
while(true) {
while(num >= v) {
sb.append_c(control[j]);
num -= v;
}
if(num <= 0) { // nonpositive input produces no output
break;
}
k = j+2;
u = v / control[k-1].digit_value();
if(control[k-1] == '2') {
k += 2;
u /= control[k-1].digit_value();
}
if(num+u >= v) {
sb.append_c(control[k]);
num += u;
} else {
j += 2;
v /= control[j-1].digit_value();
}
}
return sb.str;
} // roman()
(not extensively tested — use at your own risk. No warranty. License details here.)
Similar to a Cabot sharp, but a bit smoother. I plan to add it to my rotation for a while. I have not yet cooked with it, so have no culinary data.
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