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I would like to create a list of compiled functions and then plot them 1 by 1. To illustrate the problem (In reality the functions I want to compile are of course not x^j but some complicated matrices):

cf = Table[Compile[{{x, _Real}}, x^j], {j, 1, 3}]

as output I get a list of compiled functions. Then I would like to plot one of them, for example the second:

Plot[cf[[2]][x], {x, -1, 1}]

During evaluation of In[107]:= CompiledFunction::cfse: Compiled expression j should be a machine-size integer. >>

During evaluation of In[107]:= CompiledFunction::cfex: Could not complete external evaluation at instruction 1; proceeding with uncompiled evaluation. >>

This is a bit weird since if I compile all those functions independently (without the use of a table around Compile) I can plot them nicely.

I hope this is not just a stupid syntax error, I am quite new to mathematica so please excuse me my probably stupid question :)

Luke

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You need to use Evaluate inside the Compile call,

cf = Table[
  Compile[{{x, _Real}}, Evaluate[x^j]], {j, 1, 3}]

Plot[cf[[2]][x], {x, -1, 1}]

enter image description here

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  • $\begingroup$ @march Interesting, I get the same error as OP $\endgroup$
    – Jason B.
    Commented Feb 18, 2016 at 17:09
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    $\begingroup$ Nevermind. Didn't remove your Evaluate after copying and pasting. But Table[With[{j = j}, Compile[{{x, _Real}}, x^j]], {j, 1, 3}] still works. $\endgroup$
    – march
    Commented Feb 18, 2016 at 17:19
  • $\begingroup$ @march, that's what I would've gone with, too; With[] is handy for injecting externally-produced stuff into a compiled function. $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Feb 18, 2016 at 17:41
  • $\begingroup$ @J.M. I agree that With is great, but the fact is that I use Evaluate every single time I use Compile. I can't think of a situation where I wouldn't do do it. If it were bash I would make an alias $\endgroup$
    – Jason B.
    Commented Feb 18, 2016 at 17:55

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