gulp is not defined

[xeroxstar]

I am running this example but getting an error gulp is not defined:

const less = require('gulp-less');
const path = require('path');

gulp.task('less', function () {
    return gulp.src('./src/lib/ui/**/*.less')
        .pipe(less({
            paths: [ path.join(__dirname, 'less', 'includes') ]
        }))
        .pipe(gulp.dest('./public/css'));
});

I also tried this example:

const gulp = require('gulp');
const less = require('gulp-less');
const path = require('path');

gulp.task('less', function(){
    gulp.src('./src/lib/ui/**/*.less')
        .pipe(less())
        .pipe(gulp.dest('build'));
});

gulp.task('default', ['less']);

and i am getting and error : AssertionError [ERR_ASSERTION]: Task function must be specified

[xeroxstar]

I found this example and it worked:

const gulp = require('gulp');
const less = require('gulp-less');
const path = require('path');

gulp.task('less', function () {
    return gulp.src('./src/lib/ui/**/*.less').pipe(gulp.dest('assets/less'));
});

gulp.task('default', gulp.series('less'));