Function builtinFlatMap

builtins.go:305–346

(i *interpreter, funcv, arrv value)

}

func builtinFlatMap(i *interpreter, funcv, arrv value) (value, error) {
	fun, err := i.getFunction(funcv)
	if err != nil {
		return nil, err
	}
	switch arrv := arrv.(type) {
	case *valueArray:
		num := arrv.length()
		// Start with capacity of the original array.
		// This may spare us a few reallocations.
		// TODO(sbarzowski) verify that it actually helps
		elems := make([]*cachedThunk, 0, num)
		for counter := 0; counter < num; counter++ {
			returnedValue, err := fun.call(i, args(arrv.elements[counter]))
			if err != nil {
				return nil, err
			}
			returned, err := i.getArray(returnedValue)
			if err != nil {
				return nil, err
			}
			elems = append(elems, returned.elements...)
		}
		return makeValueArray(elems), nil
	case valueString:
		var str strings.Builder
		for _, elem := range arrv.getRunes() {
			returnedValue, err := fun.call(i, args(readyThunk(makeValueString(string(elem)))))
			if err != nil {
				return nil, err
			}
			returned, err := i.getString(returnedValue)
			if err != nil {
				return nil, err
			}
			str.WriteString(returned.getGoString())
		}
		return makeValueString(str.String()), nil
	default:
		return nil, i.Error("std.flatMap second param must be array / string, got " + arrv.getType().name)
	}
}

// builtinFlatMapArray is like builtinFlatMap, but only accepts array as the
// arrv value. Desugared comprehensions contain a call to this function, rather