- Prolog - Home
- Prolog - Introduction
- Prolog - Environment Setup
- Prolog - Hello World
- Prolog - Basics
- Prolog - Relations
- Prolog - Data Objects
- Loop & Decision Making
- Conjunctions & Disjunctions
Prolog Operators
- Prolog - Type of Operators
- Prolog - Arithmetic Comparison Operators
- Prolog - Unification Operators
- Prolog - Term Comparision Operators
- Prolog - Arithmetic Operators
- Prolog - Logical Operators
- Prolog - List Operators
- Prolog - Custom Operators
Prolog Lists
- Prolog - Lists
- Prolog - Member of List
- Prolog - Length of List
- Prolog - Concatenating Lists
- Prolog - Appending to a List
- Prolog - Deleting from a List
- Prolog - Inserting into a List
- Prolog - Permutation Operation
- Prolog - Combination Operation
- Prolog - Reverse Items of a List
- Prolog - Shift Items of a List
- Prolog - Check Order of a List
- Prolog - SubSet of a Set
- Prolog - Union of Sets
- Prolog - Intersection of Sets
- Prolog - Even and Odd Length Finding
- Prolog - Divide a List
- Prolog - Find Maximum of a List
- Prolog - Find Minimum of a List
- Prolog - Find Sum of a List
- Prolog - Sorting List using MergeSort
Built-In Predicates
- Prolog - Built-In Predicates
- Prolog - Identifying Terms
- Prolog - Decomposing Structures
- Prolog - Collecting All
- Prolog - Mathematical Predicates
- Prolog - Scientific Predicates
Miscellaneous
- Recursion and Structures
- Prolog - Backtracking
- Prolog - Preventing Backtracking
- Prolog - Different and Not
- Prolog - Inputs and Outputs
- Tree Data Structure (Case Study)
- Prolog - Examples
- Prolog - Basic Programs
- Prolog - Practical Arithmetic Examples
- Prolog - Examples of Cuts
- Towers of Hanoi Problem
- Prolog - Linked Lists
- Monkey and Banana Problem
- Prolog Useful Resources
- Prolog - Quick Guide
- Prolog - Useful Resources
- Prolog - Discussion
Prolog - Unification Operators
In prolog, = operator is a unification operator. It is used to make two items identifical by instantiating the variable as necessary. It acts as a pattern matching and assignment operator as well.
Usage
Example - Instantiating X and Y to 9.
| ?- X = 9. X = 9 yes | ?- 9 = Y. Y = 9 yes | ?-
Example - Comparing Values and Variables.
| ?- 9 = 9. yes | ?- 9 = 7. no | ?- X = Y. Y = X yes | ?-
Example - Unifying Structure.
| ?- [Head | Tail] = [1, 2, 3]. Head = 1 Tail = [2,3] yes | ?-
Non-Unifiable Operator
\= is a non-unifiable operator and returns success when the arguments cannot be unified.
Example - Non-Unifiable Operator Usage
| ?- 9 \= 7. yes | ?- 9 \= 9. no | ?- X \= 9. no | ?-
As X can be unified with a value, last expression fails.
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