An interval is represented as L...U, where L stands for the lower bound and U for the upper bound. If the upper bound is a negative number, it has to be written with an additional space, e.g., -3... -2, or in the infix notation, ...(-3, -2). The choice of using consult and not the module system is motivated by need for more flexibility.

 interval(+A, ?Res) is nondet

True if A evalutes to Res. Atoms, numbers, and strings are not evaluated. Supported operations:

• Comparison: '>', '<', '>=', '=<', '=\=', '=:='
• Basic arithemtic: addition '+', subtraction '-', division '/', multiplication '*'
• Square root for positive interval: 'interval(sqrt(A), Res)'
• Square root for negative or mixed interval: 'interval(sqrt1(A), Res)'
• Power: 'interval(A^atomic(N), Res)' or 'interval(A**atomic(N), Res)' with N being a natural number
• Exponential: 'interval(exp(A)), Res)'
• Absolute value: 'interval(abs(A), Res)'
• Sine: 'interval(sin(A), Res)'
• Unary plus: 'interval(+(A), Res)'
• Unary minus: 'interval(-(A), Res)'
• Max: 'interval(max(A, B), Res)'
• Min: 'interval(min(A, B), Res)'
• Rounding: 'interval(round(1.356...1.634, atomic(2)), Res)'

Arguments:

A	- is the expression to be evaluted.
Res	- is the result. This should always be unbound. For checking results, use 'interval(1...2 + 1, Res), Res = 2...3' instead of 'interval(1...2 + 1, 2...3)'

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 interval(Arg1, Arg2, Arg3)