https://github.com/akkartik/mu1/blob/master/058to_text.cc
 1 //: Primitive to convert any type to text (array of characters).
 2 //: Later layers will allow us to override this to do something smarter for
 3 //: specific types.
 4 
 5 :(before "End Primitive Recipe Declarations")
 6 TO_TEXT,
 7 :(before "End Primitive Recipe Numbers")
 8 put(Recipe_ordinal, "to-text", TO_TEXT);
 9 :(before "End Primitive Recipe Checks")
10 case TO_TEXT: {
11   if (SIZE(inst.ingredients) != 1) {
12     raise << maybe(get(Recipe, r).name) << "'to-text' requires a single ingredient, but got '" << to_original_string(inst) << "'\n" << end();
13     break;
14   }
15   // can handle any type
16   break;
17 }
18 :(before "End Primitive Recipe Implementations")
19 case TO_TEXT: {
20   products.resize(1);
21   products.at(0).push_back(/*alloc id*/0);
22   products.at(0).push_back(new_mu_text(inspect(current_instruction().ingredients.at(0), ingredients.at(0))));
23   break;
24 }