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pulled in lisp koans for solving

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https://github.com/google/lisp-koans
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efim
2022-07-24 12:13:42 +00:00
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;;; Copyright 2013 Google Inc.
;;;
;;; Licensed under the Apache License, Version 2.0 (the "License");
;;; you may not use this file except in compliance with the License.
;;; You may obtain a copy of the License at
;;;
;;; http://www.apache.org/licenses/LICENSE-2.0
;;;
;;; Unless required by applicable law or agreed to in writing, software
;;; distributed under the License is distributed on an "AS IS" BASIS,
;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;;; See the License for the specific language governing permissions and
;;; limitations under the License.
;;; There is a type hierarchy in Lisp, based on the set theory.
;;; An object may belong to multiple types at the same time.
;;; Every object is of type T. No object is of type NIL.
(define-test typep
;; TYPEP returns true if the provided object is of the provided type.
(true-or-false? ____ (typep "hello" 'string))
(true-or-false? ____ (typep "hello" 'array))
(true-or-false? ____ (typep "hello" 'list))
(true-or-false? ____ (typep "hello" '(simple-array character (5))))
(true-or-false? ____ (typep '(1 2 3) 'list))
(true-or-false? ____ (typep 99 'integer))
(true-or-false? ____ (typep nil 'NULL))
(true-or-false? ____ (typep 22/7 'ratio))
(true-or-false? ____ (typep 4.0 'float))
(true-or-false? ____ (typep #\a 'character))
(true-or-false? ____ (typep #'length 'function)))
(define-test type-of
;; TYPE-OF returns a type specifier for the object.
(assert-equal ____ (type-of '()))
(assert-equal ____ (type-of 4/6)))
(define-test overlapping-types
;; Because Lisp types are mathematical sets, they are allowed to overlap.
(let ((thing '()))
(true-or-false? ____ (typep thing 'list))
(true-or-false? ____ (typep thing 'atom))
(true-or-false? ____ (typep thing 'null))
(true-or-false? ____ (typep thing 't))))
(define-test fixnum-versus-bignum
;; In Lisp, integers are either fixnums or bignums. Fixnums are handled more
;; efficiently by the implementation, but some large integers can only be
;; represented as bignums.
;; Lisp converts between these two types on the fly. The constants
;; MOST-NEGATIVE-FIXNUM and MOST-POSITIVE-FIXNUM describe the limits for
;; fixnums.
(let ((integer-1 0)
(integer-2 most-positive-fixnum)
(integer-3 (1+ most-positive-fixnum))
(integer-4 (1- most-negative-fixnum)))
(true-or-false? ____ (typep integer-1 'fixnum))
(true-or-false? ____ (typep integer-1 'bignum))
(true-or-false? ____ (typep integer-2 'fixnum))
(true-or-false? ____ (typep integer-2 'bignum))
(true-or-false? ____ (typep integer-3 'fixnum))
(true-or-false? ____ (typep integer-3 'bignum))
(true-or-false? ____ (typep integer-4 'fixnum))
(true-or-false? ____ (typep integer-4 'bignum))
;; Regardless of whether an integer is a fixnum or a bignum, it is still
;; an integer.
(true-or-false? ____ (typep integer-1 'integer))
(true-or-false? ____ (typep integer-2 'integer))
(true-or-false? ____ (typep integer-3 'integer))
(true-or-false? ____ (typep integer-4 'integer))))
(define-test subtypep
(assert-true (typep 1 'bit))
(assert-true (typep 1 'fixnum))
(assert-true (typep 1 'integer))
(assert-true (typep 2 'integer))
;; The function SUBTYPEP attempts to answer whether one type specifier
;; represents a subtype of the other type specifier.
(true-or-false? ____ (subtypep 'bit 'integer))
(true-or-false? ____ (subtypep 'vector 'array))
(true-or-false? ____ (subtypep 'string 'vector))
(true-or-false? ____ (subtypep 'null 'list)))
(define-test list-type-specifiers
;; Some type specifiers are lists; this way, they carry more information than
;; type specifiers which are symbols.
(assert-true (typep (make-array 0) '(vector * 0)))
(assert-true (typep (make-array 42) '(vector * 42)))
(assert-true (typep (make-array 42 :element-type 'bit) '(vector bit 42)))
(assert-true (typep (make-array '(4 2)) '(array * (4 2))))
(true-or-false? ____ (typep (make-array '(3 3)) '(simple-array t (3 3))))
(true-or-false? ____ (typep (make-array '(3 2 1)) '(simple-array t (1 2 3)))))
(define-test list-type-specifiers-hierarchy
;; Type specifiers that are lists also follow hierarchy.
(true-or-false? ____ (subtypep '(simple-array t (3 3)) '(simple-array t *)))
(true-or-false? ____ (subtypep '(vector double-float 100) '(vector * 100)))
(true-or-false? ____ (subtypep '(vector double-float 100) '(vector double-float *)))
(true-or-false? ____ (subtypep '(vector double-float 100) '(vector * *)))
(true-or-false? ____ (subtypep '(vector double-float 100) '(array * *)))
(true-or-false? ____ (subtypep '(vector double-float 100) t)))
(define-test type-coercion
(assert-true (typep 0 'integer))
(true-or-false? ____ (typep 0 'short-float))
(true-or-false? ____ (subtypep 'integer 'short-float))
(true-or-false? ____ (subtypep 'short-float 'integer))
;; The function COERCE makes it possible to convert values between some
;; standard types.
(true-or-false? ____ (typep (coerce 0 'short-float) 'short-float)))
(define-test atoms-are-anything-thats-not-a-cons
;; In Lisp, an atom is anything that is not a cons cell. The function ATOM
;; returns true if its object is an atom.
(true-or-false? ____ (atom 4))
(true-or-false? ____ (atom '(1 2 3 4)))
(true-or-false? ____ (atom '(:foo . :bar)))
(true-or-false? ____ (atom 'symbol))
(true-or-false? ____ (atom :keyword))
(true-or-false? ____ (atom #(1 2 3 4 5)))
(true-or-false? ____ (atom #\A))
(true-or-false? ____ (atom "string"))
(true-or-false? ____ (atom (make-array '(4 4)))))
(define-test functionp
;; The function FUNCTIONP returns true if its arguments is a function.
(assert-true (functionp (lambda (a b c) (+ a b c))))
(true-or-false? ____ (functionp #'make-array))
(true-or-false? ____ (functionp 'make-array))
(true-or-false? ____ (functionp (lambda (x) (* x x))))
(true-or-false? ____ (functionp '(lambda (x) (* x x))))
(true-or-false? ____ (functionp '(1 2 3)))
(true-or-false? ____ (functionp t)))
(define-test other-type-predicates
;; Lisp defines multiple type predicates for standard types..
(true-or-false? ____ (numberp 999))
(true-or-false? ____ (listp '(9 9 9)))
(true-or-false? ____ (integerp 999))
(true-or-false? ____ (rationalp 9/99))
(true-or-false? ____ (floatp 9.99))
(true-or-false? ____ (stringp "nine nine nine"))
(true-or-false? ____ (characterp #\9))
(true-or-false? ____ (bit-vector-p #*01001)))
(define-test guess-that-type
;; Fill in the blank with a type specifier that satisfies the following tests.
(let ((type ____))
(assert-true (subtypep type '(simple-array * (* 3 *))))
(assert-true (subtypep type '(simple-array * (5 * *))))
(assert-true (subtypep type '(simple-array array *)))
(assert-true (typep (make-array '(5 3 9) :element-type 'string) type))
(assert-true (typep (make-array '(5 3 33) :element-type 'vector) type))))