In modern Prolog systems, arithmetic constraints subsume and
supersede low-level predicates over integers. The main advantage of
arithmetic constraints is that they are true relations and can be
used in all directions. For most programs, arithmetic constraints are
the only predicates you will ever need from this library.
The most important arithmetic constraint is #=/2,
which subsumes both
(is)/2 and (=:=)/2 over integers. Use #=/2
to make your programs more general. See declarative integer arithmetic (section
A.9.3).
In total, the arithmetic constraints are:
Expr1 #= Expr2 | Expr1 equals Expr2 |
Expr1 #\= Expr2 | Expr1 is not equal to Expr2 |
Expr1 #>= Expr2 | Expr1 is greater than or
equal to Expr2 |
Expr1 #=< Expr2 | Expr1 is less than or
equal to Expr2 |
Expr1 #> Expr2 | Expr1 is greater than
Expr2 |
Expr1 #< Expr2 | Expr1 is less than Expr2 |
Expr1 and Expr2 denote arithmetic
expressions, which are:
| integer | Given value |
| variable | Unknown integer |
| ?(variable) | Unknown integer |
| -Expr | Unary minus |
| Expr + Expr | Addition |
| Expr * Expr | Multiplication |
| Expr - Expr | Subtraction |
Expr ^ Expr | Exponentiation |
min(Expr,Expr) | Minimum of two expressions |
max(Expr,Expr) | Maximum of two expressions |
Expr mod Expr | Modulo induced by floored
division |
Expr rem Expr | Modulo induced by truncated
division |
abs(Expr) | Absolute value |
Expr // Expr | Truncated integer division |
| Expr div Expr | Floored integer division |
where Expr again denotes an arithmetic expression.
The bitwise operations (\)/1, (/\)/2, (\/)/2, (>>)/2,
(<<)/2, lsb/1, msb/1, popcount/1
and (xor)/2 are also supported.
