singleton variable

programming A variable which is only referred to once in a

piece of code, probably because of a programming mistake. To

be useful, a variable must be set and read from, in that

order. If it is only referred to once then it cannot be both

set and read.

There are various exceptions. C-like assignmentoperators, e.g. "x += y", read and set x and return its new

value (they are abbreviations for "x = x+y", etc). A

function argument may be passed only for the sake of

uniformity or to support future enhancements. A good

compiler or a syntax checker like lint should report

singleton variables but also allow specific instances to be

marked as deliberate by the programmer.

(1997-12-20)