31 lines
1.1 KiB
Text
31 lines
1.1 KiB
Text
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NB. In the interactive environment.
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NB. First here, Mr Babbage, we'll make the computer's words more meaningful to an english speaker.
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NB. The first is the "head" of a list, written with these inviting open arms that embrace one small dot :
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first=: {.
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NB. The small i. notation denotes "all integers up to 100000". You've already found a solution in that range.
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n=: i. 100000
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NB. This is how we write squaring.
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squareof=: *:
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NB. In our notation, a dyad is a word that takes an x value on the left and an y value on the right.
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ends=: dyad : ' x = 1000000 | y '
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NB. This dyad selects values from the list x, as marked by the list y
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where=: dyad : ' y # x '
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NB. Now that we defined our words, we can ask our question with them :
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first n where 269696 ends squareof n
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25264
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NB. With a bit of habit, you won't need to define words in english anymore.
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NB. The following easily relates word for word to the sentence we've written :
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{. (i.100000) #~ 269696 = 1000000 | *: i.100000
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25264
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NB. Like all mathematical notations, in J you see patterns that suggest simplification :
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{. I. 269696 = 1000000 | *: i.100000
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25264
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