WordPress: Template redirect

gistfile1.php

<?php
	// In functions.php

	add_action( 'template_redirect', 'redirect_template' );

	function redirect_template() {
		global $post;
		
		if ( is_single() && is_post_type( 'custompost' ) ) {
		  	wp_redirect( home_url() . '/custompost/' );
			exit;
		}
	}

	function is_post_type( $type ) {
		global $wp_query;
		
		if( $type == get_post_type( $wp_query->post->ID ) ) {
			return true;
		} else {
			return false;
		}
	}

?>