This is a trivial function, just to show that Module does not recognize the list generated by Table.
f1[x_] := Module[Table[out[i], {i, 1, Length[x]}], 42]
f1[{1, 2, 3}]
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2 Answers
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In an even more trivial case. It appears that Module is not willing to recognize such indexed variables as symbols:
f2[x_] := Module[{out[1]}, out[1] = x; out[1]]
f2[5]
Module::lvsym: Local variable specification {out[1]} contains out[1], which is not a symbol or an assignment to a symbol
Module[{out[1]}, out[1] = 5; out[1]]
answered Oct 12, 2020 at 22:48
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$\begingroup$ Correct. You can only localize symbols; not arbitrary expressions. $\endgroup$ Commented Oct 13, 2020 at 10:12
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According to the Help, ''Every time a module is evaluated, a new temporary symbol is created'' and ''Block localizes values only; it does not create new symbols''
Clear["`*"];
f1[x_] := Block[{out}, Table[out[i], {i, 1, Length[x]}, 42]]
f1[{1, 2, 3}]
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$\begingroup$ I do not understand the output of this $\endgroup$– pabloCommented Oct 14, 2020 at 11:52
Module. For example,f1[x_] := Module[{out}, Table[out[i] = x[[i]], {i, 1, Length[x]}]; out[1] + 2*out[2] + out[3]^2];thenf1[{1, 2, 3}]evaluates to14and neitheroutnor its indexed values are defined in the global name space. $\endgroup$