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18-with-match/lisplus/examples_test.py

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+"""
+Doctests for `parse`:
+
+>>> from lis import parse
+
+# tag::PARSE_DEMO[]
+>>> parse('1.5')  # <1>
+1.5
+>>> parse('set!')  # <2>
+'set!'
+>>> parse('(gcd 18 44)')  # <3>
+['gcd', 18, 44]
+>>> parse('(- m (* n (// m n)))')  # <4>
+['-', 'm', ['*', 'n', ['//', 'm', 'n']]]
+
+# end::PARSE_DEMO[]
+
+"""
+
+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))))
+(gcd 18 45)
+"""
+def test_gcd():
+    got = run(gcd_src)
+    assert got == 9
+
+
+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_newton():
+    got = run(closure_src)
+    assert got == 100