NAME
Decr — Make variable be one less.
SYNOPSIS
Decr VarName ?IntegerValue?
DESCRIPTION
Return Value
New value for variable that was decremented.
Arguments
VarNameName of variable to decrement.
IntegerValueOptional. An integer value to decrement by. Added for symmetry with incr.

For information regarding exceptions / errors, see here.
EXAMPLES 
% set x 4
4
% Decr x
3
SEE ALSO
AddTo, DivideBy, MultiplyBy, SubtractFrom, expr, incr
KEYWORDS
math, modify, variable