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Task/Babbage-problem/J/babbage-problem-2.j

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