
-Var giis +Expr

   Performs ground interval arithmetic.

Type
   library(ria)

Description
This predicate provides a way to perform interval arithmetic without setting
up constraints (i.e. the interval equivalent of is/2).

The following arithmetic expressions are supported:

+Expr
	Identity.

-Expr
	Sign change.

+-Expr
	Expr or -Expr. The result is an interval enclosing both.

abs(Expr)
	The absolute value of Expr.

E1+E2
	Addition.

E1-E2
	Subtraction.

E1*E2
	Multiplication.

E1/E2
	Division.

E1^E2
	Exponentiation.

min(E1,E2)
	Minimum.

max(E1,E2)
	Maximum.

sqr(Expr)
	Square. Logically equivalent to Expr*Expr, but with better 
	operational behaviour.

sqrt(Expr)
	Square root (always positive).

exp(Expr)
	Same as e^Expr.

ln(Expr)
	Natural logarithm, the reverse of the exp function.

sin(Expr)
	Sine.

cos(Expr)
	Cosine.

atan(Expr)
	Arcus tangens.

rsqr(Expr)
	Reverse of the sqr function. The same as +-sqrt(Expr).

rpow(E1,E2)
	Reverse of exponentiation. i.e. finds X in E1 = X^E2.

(E1;E2)
	E1 or E2. Operationally, this computes the union of two intervals.

sub(Expr)
	A subinterval of Expr.

sum(ExprList)
	Sum of a list of expressions.

min(ExprList)
	Minimum of a list of expressions.

max(ExprList)
	Maximum of a list of expressions.




