const showPage() {  if(current_user) {    return renderPage(current_user);  } else {    return showLogin();  }}const showPage() {  fromNullable(current_user)    .fold(showLogin, renderPage)}

const getPrefs = user => {  if(user.premium) {    return loadPrefs(user.preferences)  } else {    return defaultPrefs;  }}const getPrefs = user =>   (user.premium ? Right(user): Left(‘not premium‘))  .map(p => user.preferences)  .fold(    x => defaultPrefs,    x => loadPrefs(x)  )

const streetName = user => {  const address = user.address;    if(address) {    const street = address.street;        if(street) {      return street.name;    }  }  return ‘no street‘;}cosnt streetName = user =>   fromNullable(user.address)    .flatMap(address => fromNullable(address.street))    .map(street => street.name)    .fold(e => ‘no street‘, n => n)    

const concatUniq = (x, ys) => {  const found = ys.filter(y => y === x)[0]  return found ? ys : ys.concat(x);}const concatUniq = (x, ys) =>   fromNullable(ys.filter(y => y === x)[0]) // fromNullable needs value  .fold(() => ys.concat(x), y => ys)

const wrapExamples = example => {  if(example.previewPath){    try {      example.preview = fs.readFileSync(example.previewPath)    } catch(e) {          }        return example;  }}const readFile = x => tryCatch(() => readFileSync(x));const wrapExample = example =>   fromNullabel(exampe.previewPath)  .flatMap(readFile)  .fold(() => example,         ex => Object.assign({preview: p}, ex);       )

const parseDbUrl = cfg => {  try {    const c = JSON.parse(cfg);    if(c.url) {      return c.url.match(/..../)    } catch(e) {      return null    }  }}const parseDbUrl = cfg =>   tryCatch(() => JSON.parse(cfg))  .flatMap(c => fromNullable(c.url))  .fold(    e => null,    u => u.match(/..../)  )