# `sub_posn`
* Two ordered pair inputs.
* Ordered pair output.
* Subtract corresponding coordinates.
`sub_posn (5,7) (1,2) == (4,5)`
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# Dot Product
Multiply the corresponding parts and add.
`dot_product (1,3) (4,7) == 1*4 + 3*7`
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# First of
`first_of [5,1,2,3] ==`
`"The first element of [5,1,2,3] is 5."`
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# Pattern
Write a function creating this pattern.
n | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
------|:---:|:---:|:---:|:---:|:---:|:---:|:---:|
value | "a" | "b" | "c" | "ab" | "bc" | "cab" | "abbc" |
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# What?
`whaaa (a,b,c) [x:y:z:ws]@wow = `
` a : z : wow`
`whaa (5,2,1) [2,4..10] == ?`