cons

Pluralconses

Formsconses, consing, consed

1. 1
   noun

   Plural of con.

   She flies to three or four comic cons every summer to sell her artwork.

   Both cons cost retirees thousands of dollars before the police caught on.

   Note

   Paired with pros, the plural names the drawbacks weighed against a thing's advantages. Its other meanings sit lower in register: convicts is slang, while frauds, fan conventions and building conversions are informal. Programmers should not read the Lisp data structure as this plural; that is a separate word, and its own plural is conses.

2. 2
   verb

   Third-person singular simple present of con.

   The pilot cons the ship through the narrow harbor entrance.

   Every night she cons the script until she knows each line by heart.

   Note

   After he, she, it or a singular noun the present tense adds -s: he cons, but they con. In informal use it means tricking someone and takes a direct object, as in she cons tourists. Learning by heart, as with a script, is a rare meaning, knowing is obsolete, and the ship-steering use is a variant spelling of conn.

3. 3
   nouncountable

   In Lisp, a data structure made of a pair of pointers, called car and cdr, used mainly to build lists.

   A three-element list is built from three conses chained through their cdr fields.

   Calling car on a cons returns its first half.

   Note

   Every Lisp list is a chain of these cells: each holds one element in its car and the rest of the list in its cdr, until the empty list closes it off. The name is a clipping of construct, and many programmers say cons cell to keep it apart from everyday cons. The plural is conses.

4. 4
   verbtransitive

   To put an element at the front of a list by forming a cons of the element and the list, or to build up a list from conses by repeating the step.

   To add the new node, we cons it onto the front of the existing list.

   Each recursive call conses one more element onto the result.

   Similarprepend

   Note

   Programmers cons an element onto a list, and the result is a new list one item longer. The verb inflects regularly on the noun's spelling: conses, consing, consed. Peter Norvig's Paradigms of Artificial Intelligence Programming (1992) puts the idea at the heart of Lisp: a list is either the empty list or an element consed onto another list.

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