anchor.diff:      allowPrettyValues ? false
     }@args: v: with builtins;
       if      isInt      v then toString v
  -    else if isBool     v then (if v == true then "true" else "false")
  -    else if isString   v then "\"" + v + "\""
  +    else if isString   v then ''"${libStr.escape [''"''] v}"''
  +    else if true  ==   v then "true"
  +    else if false ==   v then "false"
       else if null ==    v then "null"
       else if isFunction v then
         let fna = lib.functionArgs v;
  
positive.code:               (name: value:
                  "${toPretty args name} = ${toPretty args value};") v)
          + " }"
      else abort "toPretty: should never happen (v = ${v})";
  
  }
  
negative.code:     */
    toYAML = {}@args: toJSON args;
  
  
    /* Pretty print a value, akin to `builtins.trace`.
      * Should probably be a builtin as well.
      */
  