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Given
t1 = {2, 4, 8, 16};
t2 = {1, 5, 9};
First[Select[t1, # > 1 &]]
First[Select[t1, # > 5 &]]
First[Select[t1, # > 9 &]]
can somehow be summarized by
Table[First[Select[t1, # > x &]], {x, t2}]
to get the correct result
{2, 8, 16}
Is there a way to use two pure functions connected instead of working around the problem by using Table?
Something like (which does not work!):
First[Select[t1, # > # &] & /@ t2]
Here are 2 suggestions:
First @ Select[t1, GreaterThan[#]] & /@ t2
Function[x, First @ Select[t1, # > x &]] /@ t2
Or, if you want to go really abstract:
Map[
First@Select[t1,
OperatorApplied[Function[#1 > #2]][#1]
] &,
t2
]
SelectFirst[t1, GreaterThan[#]] & /@ t2 but at some point Function is the way to go anyway.
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|-> syntax you can avoid Function e.g: (x |-> SelectFirst[t1, # > x &]) /@ t2
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Through[(SelectFirst /@ GreaterThan /@ t2) @ t1] :p
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Function, so one can do things like x|->x^2.
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Just another way to do this using GroupBy and Lookup:
Lookup[GroupBy[t1, GreaterThan[#], First] & /@ t2, True]
(*{2, 8, 16}*)
With[{x=#},SelectFirst[t1,#>x&]]&/@t2$\endgroup$#, because technically pure functions are not supposed to affect mutable state or produce different values given identical arguments, but Mathematica's 'pure' functions can do this, e.g:x = 1; f = (++x; x + #) &; {f[1],f[1],f[1]}$\endgroup$