cons

Gamma: Version 4.0
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# `cons`

`cons` -- constructs a cons cell.

## Syntax

    cons (car_exp, cdr_exp)

## Arguments

`car_exp`

  Any Gamma or Lisp expression.

`cdr_exp`

  Any Gamma or Lisp expression.

## Returns

A list whose car is `car_exp` and whose cdr is `cdr_exp`.

## Description

This function constructs a list whose car and cdr are `car_exp` and `cdr_exp` respectively. This construction is also known as a cons cell. If the `cdr_exp` is a list, this has the effect of increasing the list by one member, that is, adding the `car_exp` to the beginning of the `cdr_exp`.

## Example

        Gamma> a = list(2,3,4);
        (2 3 4)
        Gamma> b = 5;
        5
        Gamma> cons(b,a);
        (5 2 3 4)
        Gamma> cons(a,b);
        ((2 3 4) . 5)
        Gamma> cons(5,nil);
        (5)
        Gamma>

See the Start a Process section of the Common Functions for Any Progam chapter (Tutorial Two), or the Photon: Interpolator Options Widgets section of the History Functions chapter in the Cogent Tools Demo and Tutorials book for examples of this function used in context.

## See Also

Data Types and Predicates

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