8D. Arithmetic

`d0=: [: >: #:`	Add 1 to cyclic counter y with upper limit x
`d1=: +//.`	Sum items of y corresponding to keys x
`d2=: +//. {~ 'abcde'"_ i. ~.@[`	Sum y according to keys x from key set 'abcde'. (substitute your ordered keyset for 'abcde')
`d3=: +.`	Greatest common divisor of x and y
`m4=: >:@i.@(>./) \|/ ]`	1 thru max y residues of y
`m5=: 0: = m4`	Locate positive integers <: y dividing y
`d6=: +"1`	Add x to each row of y
`d7=: +`	Add list x to each column of table y
`d8=: +`	Add list y to each column of table x
`d9=: *.`	Least common multiple of x and y

JPhrases/Arithmetic