Derived class Expression_Function handles function nodes in the parse tree.

expression_function.js

class Expression_Function extends Expression {
    constructor(token, arglist) {
        super(9, token, arglist);
    }

    PrettyMath() {
        switch (this.optoken.text) {
            case 'sqrt':
                return '\\sqrt{' + this.PrettyMath_SingleArg() + '}';

            case 'abs':
                return '\\left|' + this.PrettyMath_SingleArg() + '\\right|';

            case 'cos':
            case 'sin':
                return '\\' + this.optoken.text + '\\left(' + this.PrettyMath_SingleArg() + '\\right)';

            default:
                throw {
                    name: 'FormatError',
                    message: 'Unknown function "' + this.optoken.text + '"',
                    token: this.optoken
                };
        }
    }
}