X'inhu currying u partial application?

Question

Accepted Answer

**Currying** jittrasforma funzjoni li tieħu N argumenti f'katina ta' N funzjonijiet li kull waħda tieħu argument wieħed. **Partial application** issettja *xi* argumenti issa u tirritorna funzjoni li tistenna għall-bqija.

```js
// normal
const add = (a, b, c) => a + b + c;

// curried — one argument at a time
const curriedAdd = a => b => c => a + b + c;
curriedAdd(1)(2)(3); // 6

// partial application — pre-fill some args
const add10 = curriedAdd(10);   // a is fixed at 10
add10(5)(1);                     // 16
```

Kull pass juża **closure** biex jiftakar l-argumenti ta' qabel sakemm il-ħamsa ssir pprovduta.

## Għaliex dan utli: binzja funzjonijiet speċjalizzati

```js
const log = level => message => console.log(`[${level}] ${message}`);
const error = log("ERROR");   // reusable, pre-configured logger
const info = log("INFO");
error("disk full");           // [ERROR] disk full
```

Bdil li tirrepeti l-livell kullimkien, inti tinħoloq funzjonijiet ikkonfigurati darba. Dan jiddi l-qliegh fil-pipelines funzjonali u event handlers:

```js
const onChange = field => e => setForm(f => ({ ...f, [field]: e.target.value }));
<input onChange={onChange("email")} />  // a handler specialized to "email"
```

## Curry generiku / libreriji

Libreriji (Ramda, lodash `curry`) awtomatikament-curry kwalunkwe funzjoni sabiex tista' ssupplimenta argumenti f'gruppi flessibli.

## Għaliex dan importanti

Currying tippermetti clean **function composition**, reusable configured callbacks, u point-free style.

Itt-komuni fil-codebases funzjonali u soġġett ta' intervista frekwenti biex tipprova l-fehim tal-closures.