[Caml-list] Pattern match floats

[Caml-list] Pattern match floats

[George Russell]

I am working through the OReilly book and have got as far as working on 
the little basic interpreter. I Am adding support for float type 
variables, and am trying to modify the lexer. 

I would like to be able to match ('0'..'9')*'.'('0'..'9')* i.e. one or 
more digits, a period, followed bt one or more digits.

I can't see how to do this in OCaml patter matching? Any ideas?

Thanks
George

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Re: [Caml-list] Pattern match floats

[Jean-Christophe Filliatre]

George  Russell writes:
 > I am working through the OReilly book and have got as far as working on 
 > the little basic interpreter. I Am adding support for float type 
 > variables, and am trying to modify the lexer. 
 > 
 > I would like to be able to match ('0'..'9')*'.'('0'..'9')* i.e. one or 
 > more digits, a period, followed bt one or more digits.
 > 
 > I can't see how to do this in OCaml patter matching? Any ideas?

In ocamllex, such a regular expression is written

   ['0'-'9']* '.' ['0'-'9']*    { your action, probably using 
                                  (float_of_string (lexeme lexbuf) }

Another remark: you  write "one or more digits" but  you are using the
star operation i.e. "zero, one or more digits".

Hope this helps,
-- 
Jean-Christophe Filliatre (http://www.lri.fr/~filliatr)

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