I'm trying to draw some random arrows using Metapost. For that I use a piece of code from fpast that in found at stackexchange <http://tex.stackexchange.com/questions/179745/generating-random-arrows-in-tikz/180111#180111>
Unfortunately this code does not work in context (request for a solution <http://tex.stackexchange.com/questions/225864/metapost-error-related-with-context>) because the freelabel() function. If I disable it the result is the expected. What is wrong with this code? \starttext \startMPcode numeric u, nb_vectors, wd; u := 1cm; % unit length nb_vectors := 20; wd = .5; boolean intersect; pair random_origin; color random_color; path candidate, random_vector[]; % vardef bb(expr p) = save orig, extr; pair orig, extr; orig = point 0 of p; extr = point 1 of p; pair v,w; v = wd*unitvector(extr-orig)*u; w = v rotated 90; (orig - v + w) -- (extr + v + w) -- (extr + v - w) -- (orig - v - w) -- cycle enddef; % pickup pencircle scaled 2bp; i = 1; forever: exitunless (i <= nb_vectors); intersect := false; random_length := u*(2+uniformdeviate(1)); random_angle := uniformdeviate(359); random_origin := u*(uniformdeviate(wd*nb_vectors), uniformdeviate(wd*nb_vectors)); random_color := (uniformdeviate(1), uniformdeviate(1), uniformdeviate(1)); candidate := random_origin -- (random_origin + random_length*dir(random_angle)); j := 1; forever: exitif (j = i) or (intersect = true); if bb(random_vector[j]) intersectiontimes bb(candidate) <> (-1, -1): intersect := true; fi; j := j+1; endfor; if intersect = false: random_vector[i] = candidate; drawarrow candidate withcolor random_color; freelabel(btex $v$ etex, point .5 of candidate, point .5 of candidate + dir (random_angle + 90)); i := i+1; fi; endfor; \stopMPcode \stoptext
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