Understanding Partial Application and Currying


CodeKraft

Partial application and currying are two popular concepts from functional programming and help cut code replication in certain scenarios. This article assumes an understanding of the JavaScript bind function; binding is related to partial application in JavaScript.

Partial Application

In pure functional languages, functions are not ‘invoked’, rather a set of arguments is ‘applied’ to them. Now, if all the arguments are not passed in, then the function is being  ‘partially‘ applied.

Partial application converts variadic functions (i.e. functions with multiple parameters) into functions of lesser arity by pre-specifying certain argument values.

Lets take the exponential function (x^y) from the mathematics domain as an example; an exponent value of 2 gives the square function while a value of 3 gives the cube function. The base exponential function has one of its inputs fixed to a certain value. Partial application can lead to new functions.

Currying

No, not Indian/Pakistani Curry (they taste awesome by the…

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