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less mathy stuff

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Mark Pilgrim
2009-08-04 19:23:52 -07:00
parent 99d1e77723
commit 682934c0f7
1 changed files with 4 additions and 4 deletions
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unit-testing.html
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@@ -570,9 +570,9 @@ OK</samp></pre>
result = roman5.from_roman(numeral)
self.assertEqual(integer, result)</code></pre>
<p>There&#8217;s a pleasing symmetry here. The <code>to_roman()</code> and <code>from_roman()</code> functions are inverses of each other. The first converts integers to specially-formatted strings, the second converts specially-formated strings to integers. In theory, we should be able to &#8220;round-trip&#8221; a number by passing to the <code>to_roman()</code> function to get a string, then passing that string to the <code>from_roman()</code> function to get an integer, and end up with the same number. In mathematical terms,
<p>There&#8217;s a pleasing symmetry here. The <code>to_roman()</code> and <code>from_roman()</code> functions are inverses of each other. The first converts integers to specially-formatted strings, the second converts specially-formated strings to integers. In theory, we should be able to &#8220;round-trip&#8221; a number by passing to the <code>to_roman()</code> function to get a string, then passing that string to the <code>from_roman()</code> function to get an integer, and end up with the same number.
<pre class=nd><code class=pp>x = f(g(x)) for all values of x</code></pre>
<pre class=nd><code class=pp>n = from_roman(to_roman(n)) for all values of n</code></pre>
<p>In this case, &#8220;all values&#8221; means any number between <code>1..3999</code>, since that is the valid range of inputs to the <code>to_roman()</code> function. We can express this symmetry in a test case that runs through all the values <code>1..3999</code>, calls <code>to_roman()</code>, calls <code>from_roman()</code>, and checks that the output is the same as the original input.
@@ -652,7 +652,7 @@ FAILED (failures=2)</samp></pre>
"""convert Roman numeral to integer"""
result = 0
index = 0
for numeral, integer in romanNumeralMap:
for numeral, integer in roman_numeral_map:
while s[index:index+len(numeral)] == numeral: <span class=u>&#x2460;</span>
result += integer
index += len(numeral)
@@ -667,7 +667,7 @@ FAILED (failures=2)</samp></pre>
"""convert Roman numeral to integer"""
result = 0
index = 0
for numeral, integer in romanNumeralMap:
for numeral, integer in roman_numeral_map:
while s[index:index+len(numeral)] == numeral:
result += integer
index += len(numeral)