codegithubka
diff --git a/‎02-array-seq/lispy/py3.10/examples_test.py‎
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+"""
+Doctests for `parse`
+--------------------
+
+# tag::PARSE[]
+>>> from lis import parse
+>>> parse('1.5')
+1.5
+>>> parse('ni!')
+'ni!'
+>>> parse('(gcd 18 45)')
+['gcd', 18, 45]
+>>> parse('''
+... (define double
+...     (lambda (n)
+...         (* n 2)))
+... ''')
+['define', 'double', ['lambda', ['n'], ['*', 'n', 2]]]
+
+# end::PARSE[]
+
+Doctest for `Environment`
+-------------------------
+
+# tag::ENVIRONMENT[]
+>>> from lis import Environment
+>>> inner_env = {'a': 2}
+>>> outer_env = {'a': 0, 'b': 1}
+>>> env = Environment(inner_env, outer_env)
+>>> env['a'] = 111  # <1>
+>>> env['c'] = 222
+>>> env
+Environment({'a': 111, 'c': 222}, {'a': 0, 'b': 1})
+>>> env.change('b', 333)  # <2>
+>>> env
+Environment({'a': 111, 'c': 222}, {'a': 0, 'b': 333})
+
+# end::ENVIRONMENT[]
+
+Doctests for `evaluate`
+-----------------------
+
+# tag::EVAL_NUMBER[]
+>>> from lis import parse, evaluate, standard_env
+>>> evaluate(parse('1.5'), {})
+1.5
+
+# end::EVAL_NUMBER[]
+
+# tag::EVAL_SYMBOL[]
+>>> from lis import standard_env
+>>> evaluate(parse('+'), standard_env())
+<built-in function add>
+>>> evaluate(parse('ni!'), standard_env())
+Traceback (most recent call last):
+    ...
+KeyError: 'ni!'
+
+# end::EVAL_SYMBOL[]
+
+
+# tag::EVAL_QUOTE[]
+>>> evaluate(parse('(quote no-such-name)'), standard_env())
+'no-such-name'
+>>> evaluate(parse('(quote (99 bottles of beer))'), standard_env())
+[99, 'bottles', 'of', 'beer']
+>>> evaluate(parse('(quote (/ 10 0))'), standard_env())
+['/', 10, 0]
+
+# end::EVAL_QUOTE[]
+
+# tag::EVAL_IF[]
+>>> evaluate(parse('(if (= 3 3) 1 0))'), standard_env())
+1
+>>> evaluate(parse('(if (= 3 4) 1 0))'), standard_env())
+0
+
+# end::EVAL_IF[]
+
+
+# tag::EVAL_LAMBDA[]
+>>> expr = '(lambda (a b) (* (/ a b) 100))'
+>>> f = evaluate(parse(expr), standard_env())
+>>> f  # doctest: +ELLIPSIS
+<lis.Procedure object at 0x...>
+>>> f(15, 20)
+75.0
+
+# end::EVAL_LAMBDA[]
+
+# tag::EVAL_DEFINE[]
+>>> global_env = standard_env()
+>>> evaluate(parse('(define answer (* 7 6))'), global_env)
+>>> global_env['answer']
+42
+
+# end::EVAL_DEFINE[]
+
+# tag::EVAL_DEFUN[]
+>>> global_env = standard_env()
+>>> percent = '(define (% a b) (* (/ a b) 100))'
+>>> evaluate(parse(percent), global_env)
+>>> global_env['%']  # doctest: +ELLIPSIS
+<lis.Procedure object at 0x...>
+>>> global_env['%'](170, 200)
+85.0
+
+# end::EVAL_DEFUN[]
+
+function call:
+
+# tag::EVAL_CALL[]
+>>> evaluate(parse('(% (* 12 14) (- 500 100))'), global_env)
+42.0
+
+# end::EVAL_CALL[]
+
+# tag::EVAL_SYNTAX_ERROR[]
+>>> evaluate(parse('(lambda is not like this)'), standard_env())
+Traceback (most recent call last):
+    ...
+SyntaxError: (lambda is not like this)
+
+# end::EVAL_SYNTAX_ERROR[]
+
+"""
+
+import math
+
+from lis import run
+
+
+fact_src = """
+(define (! n)
+    (if (< n 2)
+        1
+        (* n (! (- n 1)))
+    )
+)
+(! 42)
+"""
+def test_factorial():
+    got = run(fact_src)
+    assert got == 1405006117752879898543142606244511569936384000000000
+    assert got == math.factorial(42)
+
+
+gcd_src = """
+(define (mod m n)
+    (- m (* n (// m n))))
+(define (gcd m n)
+    (if (= n 0)
+        m
+        (gcd n (mod m n))))
+(display (gcd 18 45))
+"""
+def test_gcd(capsys):
+    run(gcd_src)
+    captured = capsys.readouterr()
+    assert captured.out == '9\n'
+
+
+quicksort_src = """
+(define (quicksort lst)
+    (if (null? lst)
+        lst
+        (begin
+            (define pivot (car lst))
+            (define rest (cdr lst))
+            (append
+                (quicksort
+                    (filter (lambda (x) (< x pivot)) rest))
+                (list pivot)
+                (quicksort
+                    (filter (lambda (x) (>= x pivot)) rest)))
+        )
+    )
+)
+(quicksort (list 2 1 6 3 4 0 8 9 7 5))
+"""
+def test_quicksort():
+    got = run(quicksort_src)
+    assert got == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+
+# Example from Structure and Interpretation of Computer Programs
+# https://mitpress.mit.edu/sites/default/files/sicp/full-text/sicp/book/node12.html
+
+newton_src = """
+(define (sqrt x)
+    (sqrt-iter 1.0 x))
+(define (sqrt-iter guess x)
+    (if (good-enough? guess x)
+        guess
+        (sqrt-iter (improve guess x) x)))
+(define (good-enough? guess x)
+    (< (abs (- (* guess guess) x)) 0.001))
+(define (improve guess x)
+    (average guess (/ x guess)))
+(define (average x y)
+    (/ (+ x y) 2))
+(sqrt 123454321)
+"""
+def test_newton():
+    got = run(newton_src)
+    assert math.isclose(got, 11111)
+
+
+closure_src = """
+(define (make-adder increment)
+    (lambda (x) (+ increment x))
+)
+(define inc (make-adder 1))
+(inc 99)
+"""
+def test_closure():
+    got = run(closure_src)
+    assert got == 100
+
+closure_with_change_src = """
+(define (make-counter)
+    (define n 0)
+    (lambda ()
+        (set! n (+ n 1))
+        n)
+)
+(define counter (make-counter))
+(display (counter))
+(display (counter))
+(display (counter))
+"""
+def test_closure_with_change(capsys):
+    run(closure_with_change_src)
+    captured = capsys.readouterr()
+    assert captured.out == '1\n2\n3\n'
+
+
+
+# tag::RUN_AVERAGER[]
+closure_averager_src = """
+(define (make-averager)
+    (define count 0)
+    (define total 0)
+    (lambda (new-value)
+        (set! count (+ count 1))
+        (set! total (+ total new-value))
+        (/ total count)
+    )
+)
+(define avg (make-averager))
+(avg 10)
+(avg 11)
+(avg 15)
+"""
+def test_closure_averager():
+    got = run(closure_averager_src)
+    assert got == 12.0
+# end::RUN_AVERAGER[]