Long multiplication: Difference between revisions

Line 642:

=={{header|J}}==

'''Solution:'''

<lang j> digits =: ,.&.":

polymult =: +//.@(*/)

buildDecimal=: (+ 10x&*)/@|.

~~<lang~~ j> ~~((+ 10x&*)/~~@~~|.@(,.~~&~~.":@[ +~~/~~/.@(*/)~~ ,~~.&.":@]))/~~ ,~2x^64

buildDecimal@polymult&digits/ ,~ 2x^64

340282366920938463463374607431768211456</lang>

* digits: <code>,.&.": y</code>

'''Alternatives:'''<br>

The above definition may be written as a single verb without the components:

⚫

<lang j> (+ 10x&*)/@|.@(+//.@(*/)&(,.&.":))/ ,~2x^64

⚫

340282366920938463463374607431768211456</lang>

⚫

Or using the primitive dyad <code>#.</code> instead of <code>(+ 10x&*)/@|.</code>:

<lang j> (10x&#.)@(+//.@(*/)&(,.&.":))/ ,~2x^64

⚫

340282366920938463463374607431768211456</lang>

⚫

Writing directly:

⚫

<lang j> (2x^64)*(2x^64)

340282366920938463463374607431768211456</lang>

'''Explaining the component verbs:'''

* <code>digits</code>

<lang j> ,.&.": 123

1 2 3</lang>

* ~~polynomial multiplication:~~ <code>~~x (+//.@(*/)) y~~</code> '''ref.''' [http://www.jsoftware.com/help/dictionary/samp23.htm]

* <code>polymult</code> (polynomial multiplication): '''ref.''' [http://www.jsoftware.com/help/dictionary/samp23.htm]

<lang j> 1 2 3 (+//.@(*/)) 1 2 3

1 4 10 12 9</lang>

* building the decimal result: ~~<code>(+ 10x&*)/|. y</code>~~

* <code>buildDecimal</code> (building the decimal result):

<lang j> (+ 10x&*)/|. 1 4 10 12 9

15129</lang>

⚫

or using the primitive dyad <code>#.</code> instead of <code>(+ 10x&*)/@|.</code>

⚫

<lang j> (~~10x #.~~ ,.&.":@[ +//.@(*/) ,.&.":@])/ ,~2x^64

⚫

340282366920938463463374607431768211456</lang>

⚫

Writing directly:

⚫

<lang j> (2x^64)*(2x^64)

⚫

340282366920938463463374607431768211456</lang>

=={{header|JavaScript}}==