3. Currying #

Created Thursday 25 March 2021

TODO

What is currying? #

• A curried function is a function that takes multiple arguments one at a time. All functions in the chain are different, with the contexts building up as we go inside(∵ closure).
• Function call trace is a singly linked list.

Syntax #

• Arrow functions are used, because they store state.
• Definition: Most parts are one liners, so they may be chain them directly {} for the body.
• Function invocation: f(a)(b)© also called point-free-style.

Use #

• Generate specific version of functions, by setting contexts. Example: const g = f(a)(b); we can set contexts a and b to generate g, a specialized function.

• Why do this ? - Concise code and DRY

  // Without currying function add(x, y, z) { return x + y + z } // general definition function a1§ { return 1 + 2 + z; } // no reuse function a2§ { return 10 + 20 + z; } // no reuse

  // With currying let add => x => y => z => (x + y + z); let a1 = add(1)(2); let a2 = add(10)(20); //

  // calling is the same

• Currying is highly incentivized in JS - there are even special functions which help debug curried functions.