| unifies the first argument with the value of the second argument.
?Result is +Expression
is/2 evaluates Expression and unifies Result with
the resulting value.
is/2 is a predefined infix-operator. Its priority is 700 and it is non-associative (see also current_op/3).
Arguments
Result number
Expression evaluable
Possible arguments are the following functors or operations:
(the type-representations are:
'F' means 'only floating point number'
'R' means 'floating point number or integer'
'I' means 'integer'
| Functor or operation
| Type of result
| description
|
|---|
| - F
| F
| negates a number.
| | - I
| I
| negates a number.
| | F - R
| F
| subtracts the second argument from the first one
| | R - F
| F
| subtracts the second argument from the first one
| | I - I
| I
| subtracts the second argument from the first one
| | F + R
| F
| adds two numbers
| | R + F
| F
| adds two numbers
| | I + I
| I
| adds two numbers
| | R / R
| F
| divides the first argument through the second argument
| | I // I
| I
| divides the first argument through the second argument
| | R * F
| F
| multiplies two numbers
| | F * R
| F
| multiplies two numbers
| | I * I
| I
| multiplies two numbers
| | abs(F)
| F
| absolute value of a number
| | abs(I)
| I
| absolute value of a number
| | acos(R)
| F
| arcus cosinus of a number
| | asin(R)
| F
| arcus sinus of a number
| | atan(R)
| F
| arcus tangens of a number
| | ceil(R)
| I
| rounds a number up
| | ceiling(R)
| I
| rounds a number up (same as ceil)
| | cos(R)
| F
| cosinus
| | exp(R)
| F
| exponential function of a number
| | floor(R)
| I
| rounds a number off
| | log(F)
| F
| natural logarithm of a number
| | max(R,R)
| R
| maximum of two numbers
| | min(R,R)
| R
| minimum of two numbers
| | I mod I
| I
| first argument modulo second argument
| | R ** R
| R
| first argument power second argument (same as pow)
| | pow(R,R)
| R
| first argument power second argument
| | round(R)
| I
| rounds a number
| | sin(R)
| F
| sinus of a number
| | sqrt(R)
| F
| square-root of a number
| | tan(R)
| F
| tangens of a number
| | I << I
| I
| bitwise shift left
| | I >> I
| I
| bitwise shift right
| | \ I
| I
| bitwise complement
| | I >>> I
| I
| unsigned bitwise shift right
|
Examples
| X is 15 * 2. |
Succeeds with substitution X <- 30. |
| Y is 17.5 - 2. |
Succeeds with substitution Y <- 15.5. |
| 5.0 is 5. |
Fails. |
| X is Y+4. |
instantiation_error. |
Standard
This predicate is part of the ISO-Prolog Standard.
See also
arithmetic comparison.
| 
