code: function replace(seq, value, sub, pred) {
          if (!callablep(pred))  pred = function(value, x) { return value === x }
  
          return map(seq, function(item, index) {
              return pred(value, item, index, seq)?  sub
                   : /* failed? */                   item })
      }
docs: /// Function replace /////////////////////////////////////////////////////  (seq:Sequence, value, sub[, pred:Fn]) ↦ Array  Returns an array with the elements tha match `value` replaced by `sub`.  If a predicate function is not given, the strict equality comparison (`===`) will be used.