52 lines
1.2 KiB
Forth
52 lines
1.2 KiB
Forth
A pangram is a sentence that uses all the letters in the alphabet.
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This is one way to determine if a sentence is a pangram using RETRO.
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First, define a string containing the alphabet:
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~~~
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'abcdefghijklmnopqrstuvwxyz 'FULL s:const
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~~~
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Then a blank string of the same length for the test data:
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~~~
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'__________________________ 'TEST s:const
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~~~
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Now a word to do the actual test.
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~~~
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:s:pangram? (s-f)
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'__________________________ &TEST #26 copy
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s:to-lower [ c:letter? ] s:filter
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[ dup $a - &TEST + store ] s:for-each
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&TEST &FULL s:eq? ;
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~~~
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Breaking this down, the first line:
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'__________________________ &TEST #26 copy
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Copies a blank string over the TEST string. Then:
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s:to-lower [ c:letter? ] s:filter
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Converts the string to lowercase and strips out anything that's not a
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letter. Then a quick iteration over each character:
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[ dup $a - &TEST + store ] s:for-each
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Reduces the letter to an index into the TEST string and stores the
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letter at the appropriate spot. And finally:
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&TEST &FULL s:eq? ;
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Just compares the TEST and FULL strings to get the result.
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Here's a couple of test cases:
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~~~
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'Hello_world! s:pangram?
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'The_quick_brown_fox_jumped_over_the_lazy_dogs. s:pangram?
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~~~
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