passing functions in C++

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2 total messages Started by lear@NET.BIO.NET Sat, 25 Feb 1989 00:36

#2638

Author: lear@NET.BIO.NET
Date: Sat, 25 Feb 1989 00:36

17 lines
416 bytes


I wanted arrays that would use strings as their indices.  I also
wanted a way to apply certain actions to all members of a given array.
What I would like to have is something like the following:

void MyArray::apply(int (*f)(String,String))

In English, I'd like to pass a pointer to a function.  G++ loudly
objects to the above definition.

Anyone got ideas?

Thanks in advance,
--
Eliot Lear
[lear@net.bio.net]

Re: passing functions in C++

#2640

Author: schmidt@glacier.
Date: Sat, 25 Feb 1989 03:55

35 lines
1277 bytes

In article <Feb.24.16.36.02.1989.14005@NET.BIO.NET> lear@NET.BIO.NET (Eliot Lear) writes:
++
++ I wanted arrays that would use strings as their indices.  I also
++ wanted a way to apply certain actions to all members of a given array.
++ What I would like to have is something like the following:
++
++ void MyArray::apply(int (*f)(String,String))
++
++ In English, I'd like to pass a pointer to a function.  G++ loudly
++ objects to the above definition.
++
++ Anyone got ideas?

If you change it to

  void MyArray::apply(auto int (*f)(String,String))

or use a typedef to declare the type of parameter ``f'' then G++ will
have no problems with it.  This difficulty is documented in the
g++.texinfo file and stems from g++'s use of an LALR(1) grammar to
parse the (ambiguous) C++ language.

Interestingly enough, cfront 1.2.1 also seems to have the same problem
with this particular example (properly expanded to include declaration
of class MyArray and type String, of course).

Hope this helps!

Doug
--
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