tom-weatherhead/thaw-grammar

// prolog-float-literal.ts

import { createSet, IImmutableSet } from 'thaw-common-utilities.ts';

import { IPrologExpression } from './interfaces/iprolog-expression';
import { IPrologNumber } from './interfaces/iprolog-number';
import { createSubstitution } from './prolog-substitution';

import { ISubstitution } from './interfaces/isubstitution';
import { IPrologVariable, isIPrologVariable } from './interfaces/ivariable';

const typenamePrologFloatLiteral = 'PrologFloatLiteral';

export class PrologFloatLiteral implements IPrologNumber {
    public readonly typename: string = typenamePrologFloatLiteral;
    public readonly Value: number;

    constructor(value: number) {
        this.Value = value;
    }

    public toString(): string {
        //     // E.g. If d == 13.0, we want the string to be "13.0" rather than just "13", so that we can distinguish it from an integer.
        //     // Note from Lisp: d == (tan (/ pi 4)) is a good test case; it should yield "1.0", not "1".
        //     var result = Value.ToString();

        //     if (result.IndexOf('.') < 0 && result.IndexOf('E') < 0) // I.e. If result does not contain either '.' or 'E'.
        //     {
        //         result = result + ".0";
        //     }

        //     return result;

        return `${this.Value}`;
    }

    public equals(other: unknown): boolean {
        const otherFloatLit = other as PrologFloatLiteral;

        return (
            typeof otherFloatLit !== 'undefined' &&
            otherFloatLit instanceof PrologFloatLiteral &&
            this.Value === otherFloatLit.Value
        );
    }

    public FindBindingVariables(): IImmutableSet<IPrologVariable> {
        return createSet<IPrologVariable>();
    }

    public GetListOfBindingVariables(): IPrologVariable[] {
        return [];
    }

    // eslint-disable-next-line @typescript-eslint/no-unused-vars
    public ContainsVariable(v: IPrologVariable): boolean {
        return false;
    }

    public ApplySubstitution(
        // eslint-disable-next-line @typescript-eslint/no-unused-vars
        substitution: ISubstitution
    ): IPrologExpression {
        return this;
    }

    public Unify(otherExpr: IPrologExpression): ISubstitution | undefined {
        if (this.equals(otherExpr)) {
            // Do not use "if (this == otherExpr)", which just compares references.
            return createSubstitution();
        } else if (isIPrologVariable(otherExpr)) {
            return otherExpr.Unify(this);
        }

        return undefined; // The PrologFloatLiteral and the IPrologExpression are not unifiable.
    }

    public get IsGround(): boolean {
        return true;
    }

    public EvaluateToNumber(): IPrologNumber | undefined {
        return this;
    }

    public ToInteger(): number {
        // return Convert.ToInt32(Math.Floor(Value));
        return Math.floor(this.Value);
    }

    public ToDouble(): number {
        return this.Value;
    }
}