Tacit programming is a programming paradigm in which a function definition does not include information regarding its arguments, using combinators and function composition (but not abstraction) instead of variables. The simplicity behind this idea allows its use on several programming languages, such as APL and J and especially in stack or concatenative languages, such as PostScript, Forth, Joy, and Factor. Outside of the APL and J communities, tacit programming is referred to as pointfree style,^{[1]} or more pithily as pointless programming, because of the lack of explicit arguments, or points.
The key idea in tacit programming is to assist in operating at the appropriate level of abstraction. That is, to translate the natural transformation given by currying:
 \hom(A\times B, C) \equiv \hom(A,\hom(B,C))
into computer functions, where the left represents the uncurried form of a function and the right the curried. hom(X,Y) denotes the homomorphisms from X to Y while, A x B denotes the Cartesian product of A and B.
Examples
Functional programming
A simple example (in Haskell) is a program which takes a sum of a list. A programmer might define a sum recursively using a pointed (cf. valuelevel programming) method as:
However by noting this as a fold the programmer could replace this with:
and then the argument is not needed so this can be replaced with
which is pointfree.
Another example is the use of the dot operator:
we can simply group
so
Finally to see a complex example imagine a map filter program which takes a list, applies a function to it, and then filters the elements based on a criterion
can be expressed pointfree^{[2]} as
APL family
In J, the same sort of pointfree code occurs in a function made to compute the average of a list (array) of numbers: avg=: +/ % # # counts the number of items in the array. +/ sums the items of the array. % divides the sum by the number of items
Stackbased
In stackoriented programming languages (and concatenative ones, most of which are stack based), pointfree methods are commonly used. For example a procedure to compute the Fibonacci numbers might look like:
/fib { dup dup 1 eq exch 0 eq or not { dup 1 sub fib exch 2 sub fib add } if } def
See also
References
External links
es:Programaci n t cita
