Etags (for emacs), ctags (for vi) do this. It seems to me that there was
a small package to create ml ad hoc tags in the distribution of Caml-Light
0.6 with the name mletags.

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Valérie Ménissier-Morain 
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INRIA Projets Coq & Cristal
Domaine de Voluceau -- BP 105 -- F-78153 Rocquencourt Cedex
Tel.: (33 1) (16 1) 39 63 55 98 
Fax: (33 1) (16 1) 39 63 53 30
E-mail: Valerie.Menissier@inria.fr
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Université d'Évry Val d'Essonne
Département Informatique/Mathématiques
4, Boulevard des Coquibus
91025 Évry Cedex
Tel.: (33 1) (16 1) 69 47 74 74
Fax: (33 1) (16 1) 69 47 74 72
E-mail: Valerie.Menissier-Morain@lami.univ-evry.fr
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