You need something more like the following.
You need to pass a simple list to the \foreach
loop to parse. You can't pass an array here because the list will only contain a single item: the array. Instead, just pass a list of integers to be used as indexes for accessing the arrays.
You need to use square brackets - not round - to access an indexed element of an array.
\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}[x=1cm,y=0.4cm]
\def\tabx{%
{%
0,0.01057775,0.02115551,0.03173326,0.04231101,0.05288877,0.06346652,0.07404427,%
0.08462202,0.09519978,0.1057775,0.1163553,0.126933,0.1375108,0.1480885,0.1586663,0.169244,%
0.1798218,0.1903996,0.2009773,0.2115551,0.2221328,0.2327106,0.2432883,0.2538661,0.2644438,%
0.2750216,0.2855993,0.2961771,0.3067548,0.3173326,0.3279103,0.3384881,0.3490659,0.3596436,%
0.3702214,0.3807991,0.3913769,0.4019546,0.4125324,0.4231101,0.4336879,0.4442656,0.4548434,%
0.4654211,0.4759989,%
0.4865766,0.4971544,0.5077321,0.5183099,0.5288877,0.5394654,0.5500432,0.5606209,0.5711987,0.5817764,%
0.5923542,0.6029319,0.6135097,0.6240874,0.6346652,0.6452429,0.6558207,0.6663984,0.6769762,%
0.6875539,0.6981317,0.7087095,0.7192872,0.729865,0.7404427,0.7510205,0.7615982,0.772176,%
0.7827537,0.7933315,0.8039092,0.814487,0.8250647,0.8356425,0.8462202,0.856798,0.8673757,0.8779535,%
0.8885313,0.899109,0.9096868,0.9202645,0.9308423,0.94142,0.9519978,0.9625755,0.9731533,0.983731,%
0.9943088,1.004887,1.015464,1.026042,1.03662,1.047198%
}%
}
\def\taby{%
{%
0,0.06342392,0.1265925,0.1892512,0.251148,0.3120334,0.3716625,0.4297949,0.4861967,%
0.5406408,0.5929079,0.6427876,0.690079,0.7345917,0.7761465,0.814576,0.8497254,0.8814534,0.909632,%
0.9341479,0.9549022,0.9718116,0.9848078,0.9938385,0.9988673,0.9998741,0.9968548,0.9898214,0.9788024,%
0.9638422,0.9450008,0.9223543,0.8959938,0.8660254,0.8325699,0.7957618,0.7557496,0.7126942,0.666769,%
0.618159,0.5670599,0.5136774,0.4582265,0.4009305,0.3420201,0.2817326,0.2203105,0.1580014,0.09505604,%
0.03172793,-0.03172793,-0.09505604,-0.1580014,-0.2203105,-0.2817326,-0.3420201,-0.4009305,-0.4582265,%
-0.5136774,-0.5670599,-0.618159,-0.666769,-0.7126942,-0.7557496,-0.7957618,-0.8325699,-0.8660254,%
-0.8959938,-0.9223543,-0.9450008,-0.9638422,-0.9788024,-0.9898214,-0.9968548,-0.9998741,-0.9988673,%
-0.9938385,-0.9848078,-0.9718116,-0.9549022,-0.9341479,-0.909632,-0.8814534,-0.8497254,-0.814576,%
-0.7761465,-0.7345917,-0.690079,-0.6427876,-0.5929079,-0.5406408,-0.4861967,-0.4297949,-0.3716625,%
-0.3120334,-0.251148,-0.1892512,-0.1265925,-0.06342392,-0.000000027563173%
}%
}
\coordinate (p O) at (0,0);
\foreach \i [remember=\i as \ilast (initially O), evaluate=\i as \y using {\taby[\i]}, evaluate=\i as \x using {\tabx[\i]}, evaluate=\i as \lw using \i/10] in {0,...,99}
{
\draw [red!\i, line width=\lw] (p \ilast) -- ++(\x,\y) coordinate (p \i);
}
\end{tikzpicture}
\end{document}

Note, however, that there is no point giving TikZ data to this number of decimal places. It will just increase parsing time, without improving accuracy.
EDIT
Here's an extended example in response to the request for one showing how to use a loop within a path.
\pdfminorversion=7
% ateb: http://tex.stackexchange.com/a/354419/ addaswyd o gwestiwn baptiste: http://tex.stackexchange.com/q/354406/
\documentclass[tikz,border=10pt]{standalone}
\begin{document}
\begin{tikzpicture}[x=1cm,y=0.4cm]
\def\tabx{%
{%
0,0.01057775,0.02115551,0.03173326,0.04231101,0.05288877,0.06346652,0.07404427,%
0.08462202,0.09519978,0.1057775,0.1163553,0.126933,0.1375108,0.1480885,0.1586663,0.169244,%
0.1798218,0.1903996,0.2009773,0.2115551,0.2221328,0.2327106,0.2432883,0.2538661,0.2644438,%
0.2750216,0.2855993,0.2961771,0.3067548,0.3173326,0.3279103,0.3384881,0.3490659,0.3596436,%
0.3702214,0.3807991,0.3913769,0.4019546,0.4125324,0.4231101,0.4336879,0.4442656,0.4548434,%
0.4654211,0.4759989,%
0.4865766,0.4971544,0.5077321,0.5183099,0.5288877,0.5394654,0.5500432,0.5606209,0.5711987,0.5817764,%
0.5923542,0.6029319,0.6135097,0.6240874,0.6346652,0.6452429,0.6558207,0.6663984,0.6769762,%
0.6875539,0.6981317,0.7087095,0.7192872,0.729865,0.7404427,0.7510205,0.7615982,0.772176,%
0.7827537,0.7933315,0.8039092,0.814487,0.8250647,0.8356425,0.8462202,0.856798,0.8673757,0.8779535,%
0.8885313,0.899109,0.9096868,0.9202645,0.9308423,0.94142,0.9519978,0.9625755,0.9731533,0.983731,%
0.9943088,1.004887,1.015464,1.026042,1.03662,1.047198%
}%
}
\def\taby{%
{%
0,0.06342392,0.1265925,0.1892512,0.251148,0.3120334,0.3716625,0.4297949,0.4861967,%
0.5406408,0.5929079,0.6427876,0.690079,0.7345917,0.7761465,0.814576,0.8497254,0.8814534,0.909632,%
0.9341479,0.9549022,0.9718116,0.9848078,0.9938385,0.9988673,0.9998741,0.9968548,0.9898214,0.9788024,%
0.9638422,0.9450008,0.9223543,0.8959938,0.8660254,0.8325699,0.7957618,0.7557496,0.7126942,0.666769,%
0.618159,0.5670599,0.5136774,0.4582265,0.4009305,0.3420201,0.2817326,0.2203105,0.1580014,0.09505604,%
0.03172793,-0.03172793,-0.09505604,-0.1580014,-0.2203105,-0.2817326,-0.3420201,-0.4009305,-0.4582265,%
-0.5136774,-0.5670599,-0.618159,-0.666769,-0.7126942,-0.7557496,-0.7957618,-0.8325699,-0.8660254,%
-0.8959938,-0.9223543,-0.9450008,-0.9638422,-0.9788024,-0.9898214,-0.9968548,-0.9998741,-0.9988673,%
-0.9938385,-0.9848078,-0.9718116,-0.9549022,-0.9341479,-0.909632,-0.8814534,-0.8497254,-0.814576,%
-0.7761465,-0.7345917,-0.690079,-0.6427876,-0.5929079,-0.5406408,-0.4861967,-0.4297949,-0.3716625,%
-0.3120334,-0.251148,-0.1892512,-0.1265925,-0.06342392,-0.000000027563173%
}%
}
\coordinate (p O) at (0,0);
\foreach \i [remember=\i as \ilast (initially O), evaluate=\i as \y using {\taby[\i]}, evaluate=\i as \x using {\tabx[\i]}, evaluate=\i as \lw using \i/10] in {0,...,99}
{
\draw [red!\i, line width=\lw] (p \ilast) -- ++(\x,\y) coordinate (p \i);
}
\draw [green!75!black] (0,-1) \foreach \i [evaluate=\i as \y using {\taby[\i]}, evaluate=\i as \x using {\tabx[\i]}] in {0,...,99} { -- ++(\x,\y) };
\draw (0,-2) coordinate (p O) \foreach \i [remember=\i as \ilast (initially O), evaluate=\i as \y using {\taby[\i]}, evaluate=\i as \x using {\tabx[\i]}, evaluate=\i as \lw using \i/10] in {0,...,99}
{
(p \ilast) edge [blue!\i, line width=\lw] coordinate [pos=1] (p \i) ++(\x,\y)
};
\end{tikzpicture}
\end{document}
The red curve uses a loop over paths, one per iteration, as before. The lower green and blue curves use loops within paths, one per coordinate.

The green curve has to use the same options for all parts of the path, so the colour and width are static. In this case, we don't need to remember coordinates by naming them, because we are drawing a continuous path and are wherever we've got to.
The blue curve works around the same-options restriction by using the edge
operation, which breaks off the current path to make a diversion. In this case, however, we are back to needing to remember the coordinates by naming them, as the path resumes from where it began when the edge
is complete.
tabx
supposed to be\tabx
? But it is just a single item, I think, as you've enclosed it in brackets. I don't think you can loop through an array directly like that.