prolog-arithmetic

Explain Prolog is/2 evaluation, arithmetic comparisons, and CLP(FD) constraints.

1|Updated Mar 15, 2026

Search Tags:#arithmetic #constraint-solving #prolog #is/2 #clpfd #peano

Ready to run

npx skills add https://github.com/hafley66/claude-research --skill prolog-arithmetic

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: prolog-arithmetic
Source: https://github.com/hafley66/claude-research/tree/main/skills/prolog-arithmetic
Command: npx skills add https://github.com/hafley66/claude-research --skill prolog-arithmetic

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Prolog developers often struggle to reason about numeric expressions, operator semantics, and constraint solving. This skill clarifies is/2 evaluation, arithmetic comparisons, and CLP(FD) constraints, bridging symbolic terms and numerical results.

Core Features & Use Cases

Explains how is/2 evaluates the right-hand side and unifies with the left-hand side, including groundness requirements.
Demonstrates arithmetic comparison operators and CLP(FD) constraint propagation for bidirectional reasoning.
Provides Peano arithmetic examples to illustrate purely logical definitions of numbers and their practical limits.

Quick Start

Try evaluating a Prolog arithmetic expression using is/2, for example set X is 3 + 4 and return X.

Frequently Asked Questions about prolog-arithmetic

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How does the Prolog is/2 operator evaluate arithmetic expressions?▼

The Prolog is/2 operator evaluates the arithmetic expression on its right-hand side and unifies the numerical result with the left-hand side. This requires the right-hand side to be fully instantiated with ground numeric values before evaluation can proceed.

What is CLP(FD) constraint propagation in Prolog?▼

CLP(FD) in Prolog is a constraint solving technique that enables bidirectional reasoning over integers. It propagates arithmetic constraints across variables without requiring them to be fully instantiated, supporting logical and numerical problem solving.

How do I implement natural numbers using Peano arithmetic in Prolog?▼

Peano arithmetic in Prolog defines natural numbers using symbolic terms like zero and successor representations. It illustrates purely logical definitions of numbers, demonstrating their practical limits and differences from standard numeric evaluation.

What is the difference between Prolog arithmetic comparisons and is/2 evaluation?▼

Prolog arithmetic comparisons evaluate both sides numerically before checking relational operators, whereas is/2 evaluates the right-hand side and unifies the result with a left-hand side variable. Comparisons do not require unification output.

Why does my Prolog arithmetic expression fail with an instantiation error?▼

Prolog arithmetic evaluation fails with an instantiation error when using is/2 with ungrounded variables on the right-hand side. The operator requires all numeric arguments to be fully instantiated before it can compute the result and unify.

Can I use CLP(FD) constraints for bidirectional arithmetic reasoning in Prolog?▼

Yes, CLP(FD) constraints support bidirectional arithmetic reasoning in Prolog by propagating constraints across variables. This allows the system to infer variable values and narrow domains without needing fully ground numeric inputs beforehand.