tom-weatherhead/thaw-grammar

// graph-reduction.ts

import { IExpression } from '../../common/domain-object-model/iexpression';
import { ISExpression } from '../../languages/lisp/domain-object-model/isexpression';

import { SExpressionBase } from '../lisp/domain-object-model/sexpression-base';

// #region SKIOp

const typenameSKIOp = 'SKIOp';

export function isSKIOp(obj: unknown): obj is SKIOp {
    return (obj as SKIOp).typename === typenameSKIOp;
}

export class SKIOp extends SExpressionBase {
    public readonly expectedNumArgs: number;
    public readonly typename = typenameSKIOp;

    constructor(public readonly name: string) {
        super();

        switch (name) {
            case 'S':
                this.expectedNumArgs = 3;
                break;

            case 'K':
                this.expectedNumArgs = 2;
                break;

            case 'I':
                this.expectedNumArgs = 1;
                break;

            default:
                throw new Error(`SKIOp constructor: Invalid name '${name}'`);
        }
    }

    public toString(): string {
        return this.name;
    }

    // public evaluate(): IExpression<ISExpression> {
    //     throw new Error('SKIOps cannot be evaluated; they must be reduced');
    // }
    //
    // public asValue(): IExpression<ISExpression> | undefined {
    //     return undefined;
    // }
}

// #endregion

// An interior (non-leaf) node of the graph.

const typenameGraphReductionNode = 'GraphReductionNode';

export function isGraphReductionNode(obj: unknown): obj is GraphReductionNode {
    const otherNode = obj as GraphReductionNode;

    return (
        typeof otherNode !== 'undefined' &&
        typeof otherNode.typename !== 'undefined' &&
        otherNode.typename === typenameGraphReductionNode
    );
}

export class GraphReductionNode extends SExpressionBase {
    public readonly typename = typenameGraphReductionNode;

    constructor(
        public leftChild: IExpression<ISExpression>,
        public rightChild: IExpression<ISExpression>
    ) {
        super();

        if (typeof leftChild === 'undefined') {
            throw new Error('GraphReductionNode constructor: leftChild is undefined');
        } else if (typeof rightChild === 'undefined') {
            throw new Error('GraphReductionNode constructor: rightChild is undefined');
        }
    }

    public toString(): string {
        return `(${this.leftChild} ${this.rightChild})`;
    }

    // public evaluate(): IExpression<ISExpression> {
    //     // NotImplementedException
    //     throw new Error('GraphReductionNode.evaluate()');
    // }

    // public asValue(): IExpression<ISExpression> | undefined {
    //     return undefined;
    // }
}