str/src/vm/commands/lower.ts

import {Command, ParseContext} from "./command.js";
import {LexInput} from "../lexer.js";
import {Awaitable} from "../../util/types.js";
import {StrVM} from "../vm.js";

export class Lower extends Command<{}> {
    isParseCandidate(token: LexInput): boolean {
        return this.isKeyword(token, 'lower')
    }

    attemptParse(context: ParseContext): {} {
        return {}
    }

    getDisplayName(): string {
        return 'lower'
    }

    execute(vm: StrVM): Awaitable<StrVM> {
        return vm.inPlace(ctx =>
            ctx.replaceSubject(sub =>
                sub.modify(s => s.toLowerCase())))
    }
}