问题
The following Mathematica function f creates a string of whitespace of length n.
f[n_]:=Fold[StringJoin,"",Array[" "&,n]]
There must be a zillion alternatives to create this function.
How would you have done it?
回答1:
f[n_] := StringJoin @ ConstantArray[" ", n]
Edit: since @ is as idiomatic as @@ and a bit faster (thanks to Mr.Wizard for benchmarking) and shorter i updated the solution.
回答2:
f[n_] := FromCharacterCode[ConstantArray[32, {n}]]
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回答3:
f[n_] := StringJoin[Table[" ", {n}]]
回答4:
Spacer and Invisible are also be useful for creating whitespace, with differences in how you specify the size of the space.
回答5:
f = ConstantArray[" ", #] <> "" &;
This is about twice as fast as Thies Heidecke's function, but not nearly as fast as Sjoerd's.
For large n a longer initial string is helpful. This is faster than Sjoerd's method for n > 10000:
f2ss = " "~ConstantArray~499 <> "";
f2[n_ /; n < 500] := StringTake[f2ss, n]
f2[n_ /; n < 5000] := StringTake[ConstantArray[" ", ⌈n/10⌉] <> "", n]
f2[n_] := StringTake[ConstantArray[f2@400, ⌈n/400⌉] <> "", n]
来源：https://stackoverflow.com/questions/6082172/creating-a-variable-length-string-of-whitespaces-in-mathematica