This library does partial application, not currying

[timfennis]

Like the title says, the examples in the documentation are examples of partial application. Currying is when a function with 4 arguments is turned in to a function with 1 argument that produces a function with 1 argument that produces a function with 1 argument that produces a function with 1 argument that produces the result.

https://en.wikipedia.org/wiki/Currying

[mathiasverraes]

the examples in the documentation are examples of partial application

Agreed.

Currying is when a function with 4 arguments is turned in to a function with 1 argument that produces a function with 1 argument that produces a function with 1 argument that produces a function with 1 argument that produces the result.

Agreed.

This library does partial application, not currying

I'd say it does both, and it uses the same curry function for both.

As I was writing a test to explore the behaviour, I also discovered that partial application requires an additional () when you pass all the arguments. Not a big deal, but still a bug imho.

<?php

use PHPUnit\Framework\TestCase;
use function Cypress\Curry\curry;

final class CurryTest extends TestCase
{
    /** @test */
    public function curry()
    {
        $f = fn($a, $b, $c) => $a + $b + $c;
        $curried = curry($f);

        $this->assertIsCallable($curried);
        $this->assertIsCallable($curried(1));
        $this->assertIsCallable($curried(1)(2));
        $this->assertIsCallable($curried(1)(2));

        $this->assertEquals(6, $curried(1)(2)(3));
    }

    /** @test */
    public function partial_application()
    {
        $f = fn($a, $b, $c) => $a + $b + $c;

        $this->assertIsCallable(curry($f, 1));
        $this->assertIsCallable(curry($f, 1, 2));

        // I would expect this:
        $this->assertEquals(6, curry($f, 1, 2, 3));

        // But we must add a () at the end, which I feel is a bug:
        $this->assertIsCallable(curry($f, 1, 2, 3));
        $this->assertEquals(6, curry($f, 1, 2, 3)());
    }
}