LSOperator Enumeration¶

class
localsolver.
LSOperator
¶ Mathematical operators available for modeling. These operators are used to type the expressions created in LocalSolver mathematical optimization model.
As other enumerations present in the localsolver module, LSOperator is enumerable and indexable:
print (LSOperator[0]) # Shows LSOperator.BOOL print (LSOperator.BOOL.value) # Shows 0 # Iterates over the members of LSOperator for e in LSOperator: print e

BOOL
¶ Boolean decision. Decisional operator with no operand. Decision variable with domain
{0,1}
.

FLOAT
¶ Float decision. Operator with two operands that represent the lower bound and the upper bound of the decision (domain [lb, ub]). The bounds must be constants (integers or doubles).
Since: 4.0

CONST
¶ Constant. Unary operator. Can be equal to any integer. Note that constants 0 or 1 are considered as boolean. Constants are implicitly created when passing integer arguments to
LSModel.create_expression()
orLSExpression.add_operand()
.

SUM
¶ Sum. Nary arithmetic operator.
SUM(e1, e2, ..., eN)
is equal to the sum of all operandse1, e2, ..., eN
. This operator returns an integer if all the operands are booleans or integers and a double as soon as one operand is a double.With collections (lists, sets) or ranges
This operator can also be used with
RANGE
,LIST
orSET
to create expressions with a dynamic number of operands. In that case, this operator becomes a binary operator that takes a range, a list or a set as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range, list or set and will sum all the values computed and returned by the function.

SUB
¶ Substraction. Binary arithmetic operator.
SUB(x, y)
is equal to the value ofx  y
. This operator returns an integer or a double according to the type of its operands.Since: 4.0

PROD
¶ Product. Nary arithmetic operator.
PROD(e1, e2, ..., eN)
is equal to the product of all operandse1, e2, ..., eN
. This operator returns an integer if all the operands are booleans or integers, and a double as soon as one operand is a double.With collections (lists, sets) or ranges
This operator can also be used with
RANGE
,LIST
orSET
to create expressions with a dynamic number of operands. In that case, this operator becomes a binary operator that takes a range, a list or a set as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range, list or set and will compute the product of all the values returned by the function.

MAX
¶ Maximum. Nary arithmetic operator.
MAX(e1, e2, ..., eN)
is equal to the maximum value among all operandse1, e2, ..., eN
. This operator returns an integer if all the operands are booleans or integers, and a double as soon as one operand is a double.With collections (lists, sets) or ranges
This operator can also be used with
RANGE
,LIST
orSET
to create expressions with a dynamic number of operands. In that case, this operator becomes a binary operator that takes a range, a list or a set as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range, list or set and will find the maximum value among all the values returned by the function.

MIN
¶ Minimum. Nary arithmetic operator.
MIN(e1, e2, ..., eN)
is equal to the minimum value among all operandse1, e2, ..., eN
. This operator returns an integer if all the operands are booleans or integers, and a double as soon as one operand is a double.With collections (lists, sets) or ranges
This operator can also be used with
RANGE
,LIST
orSET
to create expressions with a dynamic number of operands. In that case, this operator becomes a binary operator that takes a range, a list or a set as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range, list or set and will find the minimum value among all the values returned by the function.

EQ
¶ Equal. Binary relational operator.
EQ(a, b) = 1
ifa == b
, and 0 otherwise. This operator returns a boolean.

NEQ
¶ Not equal to. Binary relational operator.
NEQ(a,b) = 1
ifa != b
, and 0 otherwise. This operator returns a boolean.

GEQ
¶ Greater than or equal to. Binary relational operator. GEQ(a,b) = 1 if a >= b, and 0 otherwise. This operator returns a boolean.

LEQ
¶ Lower than or equal to. Binary relational operator.
LEQ(a,b) = 1
ifa <= b
, and 0 otherwise. This operator returns a boolean.

GT
¶ Strictly greater than. Binary relational operator.
GT(a,b) = 1
ifa > b
, and 0 otherwise. This operator returns a boolean.

LT
¶ Strictly lower than. Binary relational operator.
LQ(a, b) = 1
ifa < b
, and 0 otherwise. This operator returns a boolean.

IF
¶ IfThenElse. Ternary conditional operator.
IF(a,b,c)
is equal to b if a is true, and c otherwise. Note that the first operand must be a boolean (that is, equal to 0 or 1). This operator returns a boolean, an integer or a double according to the type of the second and third operands.

NOT
¶ Not. Unary logical operator.
NOT(a) = 1  a
. Note that the operand must be boolean (that is, equal to 0 or 1). This operator returns a boolean.

AND
¶ And. Nary logical operator.
AND(e1, e2, ..., eN)
is equal to 1 (true) if all the operandse1, e2, ..., eN
are 1, and 0 otherwise. All the operands must be boolean (that is, equal to 0 or 1). This operator returns a boolean.With collections (lists, sets) or ranges
This operator can also be used with
RANGE
,LIST
orSET
to create expressions with a dynamic number of operands. In that case, this operator becomes a binary operator that takes a range, a list or a set as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range, list or set and will return 1 if all the values returned by the function are 1 and 0 otherwise.

OR
¶ Or. Nary logical operator.
OR(e1, e2, ..., eN)
is equal to 0 (false) if all operandse1, e2, ..., eN
are 0, and 1 otherwise. All the operands must be boolean (that is, equal to 0 or 1). This operator returns a boolean.With collections (lists, sets) or ranges
This operator can also be used with
RANGE
,LIST
orSET
to create expressions with a dynamic number of operands. In that case, this operator becomes a binary operator that takes a range, a list or a set as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range, list or set and will return 0 if all the values returned by the function are 0 and otherwise.

XOR
¶ Exclusive or (also called “xor”). Nary logical operator.
XOR(e1, e2, ..., eN)
is equal to 0 if the number of operands with value 1 amonge1, e2, ..., eN
is even, and 1 otherwise. Remarkable case:XOR(a,b) = 1
ifa == b
, and0
otherwise. All the operands must be boolean (that is, equal to 0 or 1). This operator returns a boolean.With collections (lists, sets) or ranges
This operator can also be used with
RANGE
,LIST
orSET
to create expressions with a dynamic number of operands. In that case, this operator becomes a binary operator that takes a range, a list or a set as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range, list or set and will return 0 if the number of value 1 returned by the function is even, and 1 otherwise.

ABS
¶ Absolute value. Unary arithmetic operator.
ABS(e) = e >= 0 ? e : e
. This operator returns an integer or a double according to the type of its operand.

DIST
¶ Distance between two numbers. Binary arithmetic operator.
DIST(a,b) = ABS(ab)
. This operator returns an integer or a double according to the type of its operands.

DIV
¶ Division. Binary arithmetic operator. This operator always returns a double. Note that until version 4.0, the division was an integer division if both operands were integers.

MOD
¶ Modulo (remainder of the integer division). Binary arithmetic operator.
MOD(a, b) = r
such thata = q * b + r
withq
,r
integers, wherer
,a
have the same sign andr < b
. Note that the operands must be integers. This operator returns an integer. Be careful: whena > 0
andb < 0
, the value computed byMOD(a, b)
differs from the evaluation ofa%b
in python.

ARRAY
¶ Array. An array is a collection of elements. Indexes begin at 0. It could be used with operators like
AT
orSCALAR
. An array doesn’t have a value by itself, but can contain operands of type boolean, integer, double, array (for multidimensional arrays) or collection (list or set). In the latter case, the collections must share the same domain and same type (either list or set). All the elements of an array must be of the same type.With ranges
This operator can also be used with
RANGE
to create an array with a dynamic number of elements. In that case, this operator becomes a binary operator that takes a range as first operand and aLAMBDA_FUNCTION
as second operand. The operator will call the function on each value of the range and the returned values will be used to populate the array.Since: 2.1

AT
¶ Returns the element at specific coordinates of an array or a list.
For arrays
The first operand must be the array and the other operands must be the coordinates of the element to get. The number of coordinates depends on the dimension of the array. Thus AT(myArray, i) returns the i element of the onedimensional array myArray. This operator returns a boolean, an integer or a double according to the type of the operands in the array. If one of the specified coordinate is out of range, the evaluation of the expression will fail.
For lists
The first operand must be the list and the second operand must be the index of the element to get. If the index is out of range (index < 0 or index > count(list)), the evaluation of the expression will not fail but will return 1.
Since: 2.1

SCALAR
¶ Scalar product.
SCALAR(a, x) = sum(a[i]*x[i])
with a and x two arrays. This operator returns an integer or a double according to the type of the operands in the arrays.Since: 2.1

CEIL
¶ Ceil. Unary arithmetic operator. Returns a value rounded to the next highest integer. This operator returns an integer.
Since: 3.0

FLOOR
¶ Floor. Unary arithmetic operator. Returns a value rounded to the next lowest integer. This operator returns an integer.
Since: 3.0

ROUND
¶ Round. Unary arithmetic operator. Returns a value rounded to the nearest integer. This operator returns an integer.
Since: 3.0

SQRT
¶ Square root. Unary arithmetic operator. This operator returns a double.
Since: 3.0

LOG
¶ Natural logarithm (basee). Unary arithmetic operator. This operator returns a double.
Since: 3.0

EXP
¶ Basee exponential. Unary arithmetic operator. This operator returns a double.
Since: 3.0

POW
¶ Power operator.
POW(x, y)
is equals to the value of x to the power of y. This operator returns a double.Since: 3.0

COS
¶ Cosine. Unary arithmetic operator. This operator returns a double.
Since: 3.0

SIN
¶ Sine. Unary arithmetic operator. This operator returns a double.
Since: 3.0

TAN
¶ Tangent. Unary arithmetic operator. This operator returns a double.
Since: 3.0

INT
¶ Integer decision variable. Decisional operator with two operands min and max. Decision variable with domain
[min,max]
.Since: 5.0

PIECEWISE
¶ Piecewiselinear function operator. The piecewise linear function is defined by two arrays of numbers giving the breakpoints of the function. This operator has exactly 3 operands: The first two operands must be two arrays of equal lengths (necessarily larger or equal to 2). These arrays must contain constant numbers (int or double). The first array must contain numbers in ascending order. The third operand must be an integer or double expression. An exception will be thrown if its value is strictly smaller that the first element of the first array, or strictly larger than the last element of the first array. This operator returns a double.
PIECEWISE(x,y,z)
returns the image of z by the function defined by geometric points(x[0], y[0]), (x[1], y[1]), ..... (x[n1], y[n1])
, For instancePIECEWISE({0, 50, 100}, {0, 10, 100}, 75)
returns 55.Discontinuities are allowed in the definition of the function, that is to say that two geometric points can share the same xcoordinate. By convention the value taken by the function at such a discontinuous point is the one associated to the last occurrence of this xcoordinate in array x. For instance
PIECEWISE({0, 50, 50, 100},{0, 0.1, 0.9, 1}, 50)
returns 0.9;Since: 5.0

LIST
¶ A list is an ordered collection of integers within a domain
[0, n1]
wheren
is the unique argument of this operator. Mathematically a list is a permutation of a subset of[0, n1]
. This operator takes exactly one operand: a strictly positive integer constant. All values in the list will be pairwise different, non negative and strictly smaller that this number.The elements of the list can be accessed individually with the operator
AT
.

COUNT
¶ The number of elements in a collection. This operator takes exactly one argument of type list.
Since: 5.5

INDEXOF
¶ The index of a value in a list (1 if the value is not in the list). This operator takes exactly two arguments: the first one is a list, the second one is an integer expression.
Since: 5.5

PARTITION
¶ Partition. Nary logical operator.
PARTITION(c1, c2, ..., cN)
is true if all lists or setsc1, c2, ..., cN
form a partition of their common domain. All the operands must be collections of the same type (either list or set) and on the same range. These collections can be stored in a LSArray that will be passed as argument of the partition:PARTITION(array(c1, c2, ..., cN))
.Since: 5.5

DISJOINT
¶ Disjoint. Nary logical operator.
DISJOINT(c1, c2, ..., cN)
is true if all lists or setsc1, c2, ..., cN
are pairwise disjoint. All the operands must be collections of the same type (either list or set) and on the same range. These collections can be stored in a LSArray that will be passed as argument of the disjoint:DISJOINT(array(c1, c2, ..., cN))
.Since: 5.5

COVER
¶ Cover. Nary logical operator.
COVER(c1, c2, ..., cN)
is true if all values in the domain are at least in one list or setc1, c2, ..., cN
. All the operands must be collections of the same type (either list or set) and on the same range. These collections can be stored in a LSArray that will be passed as argument of the cover:COVER(array(c1, c2, ..., cN))
.Since: 10.5

FIND
¶ Find.
find(a, v)
returns the position of the collection in the arraya
that contains the valuev
. If the value is not in any collections of the array, it returns 1. This operator takes exactly two arguments: the first one is anARRAY
of collections, the second one is the value searched. All the collections of the array must be of same type and on the same range.Since: 10.5

EXTERNAL_FUNCTION
¶ External function.
External functions are used to retrieve the value of expressions from external functions written with your favorite language. External functions are created with the dedicated methods
LSModel.create_int_external_function()
orLSModel.create_double_external_function()
.Since: 9.5

CALL
¶ Call a particular function.
The first operand must be a function (like
EXTERNAL_FUNCTION
,BLACKBOX_FUNCTION
or : attr:LAMBDA_FUNCTION.). The other operands are passed to the function as arguments.Since: 6.0

LAMBDA_FUNCTION
¶ Lambda function. Lambda functions are created with the dedicated method
LSModel.create_lambda_function()
.Since: 9.5

ARGUMENT
¶ Argument of a function. Arguments are automatically and implicitely created when you create a function with method
LSModel.create_function()
.Since: 7.0

RANGE
¶ Range expression. This operator takes exactly two integer operands. The first one is the lower bound (inclusive), the second one is the upper bound (exclusive).
A range doesn’t have a value by itself but can be used with Nary operators like
SUM
,PROD
,MIN
,MAX
,OR
,AND
,XOR
orARRAY
to create expressions that have a dynamic number of operands.Since: 7.0

CONTAINS
¶ Contains.
contains(l, v)
is true if and only if the listl
contains the valuev
. This operator takes exactly two arguments: the first one is a list, the second one is an integer expression.Since: 7.5

SET
¶ A set is an unordered collection of integers within a range [0, n1] where n is the unique argument of this operator. This operator takes exactly one operand: a strictly positive integer constant. All values in the set will be pairwise different, non negative and strictly smaller that this number. Contrary to the
LIST
operator, elements in a set are not ordered and cannot be indexed withAT
. Sets can only be manipulated with lambdas and nary operators likeSUM
,MIN
,AND
, …Since: 8.0

BLACKBOX_FUNCTION
¶ Blackbox function. Blackbox functions can be used to optimize functions that are computationally expensive. For more information, please see the modeling features.
Since: 9.5
