(defpackage #:aoc
  (:use :cl)
  (:export :with-lines :all))

(in-package #:aoc)

(defmacro with-lines ((stream var) &body body)
  "Loop over the lines of STREAM, executing BODY. This exposes the
variable VAR and the argument-less function NEXT-LINE to the lexical
environment."
  (let ((next-line-p (member 'next-line (alexandria:flatten body))))
    `(loop :for ,var := (read-line ,stream nil)
           :while (not (null ,var))
           :do ,(if next-line-p
                    `(flet ((next-line ()
                              (setf ,var (read-line ,stream nil))))
                       ,@body)
                    `(progn
                       ,@body)))))

(defun all (predicate list)
  (loop :for e :in list
        :with all := t
        :do (setf all (and all (funcall predicate e)))
        :finally (return all)))