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Do function arguments invoke a function?

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  Do function arguments invoke a function? Chad <cdalten@gmail.com> - 2015-10-04 02:15 -0700
    Re: Do function arguments invoke a function? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-04 08:09 -0400
      Re: Do function arguments invoke a function? Chad <cdalten@gmail.com> - 2015-10-04 13:52 -0700
        Re: Do function arguments invoke a function? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-04 17:13 -0400
        Re: Do function arguments invoke a function? James Kuyper <jameskuyper@verizon.net> - 2015-10-04 17:13 -0400
        Re: Do function arguments invoke a function? Geoff <geoff@invalid.invalid> - 2015-10-04 17:09 -0700
        Re: Do function arguments invoke a function? Geoff <geoff@invalid.invalid> - 2015-10-04 17:10 -0700
          Re: Do function arguments invoke a function? Chad <cdalten@gmail.com> - 2015-10-04 19:50 -0700
            Re: Do function arguments invoke a function? James Kuyper <jameskuyper@verizon.net> - 2015-10-05 00:26 -0400
    Re: Do function arguments invoke a function? James Kuyper <jameskuyper@verizon.net> - 2015-10-04 12:59 -0400
      Re: Do function arguments invoke a function? James Kuyper <jameskuyper@verizon.net> - 2015-10-04 14:36 -0400
    Re: Do function arguments invoke a function? jacobnavia <jacob@jacob.remcomp.fr> - 2015-10-04 19:26 +0200
    Re: Do function arguments invoke a function? Keith Thompson <kst-u@mib.org> - 2015-10-04 15:36 -0700
    Re: Do function arguments invoke a function? Rosario19 <Ros@invalid.invalid> - 2015-10-05 05:49 +0200

#71794 — Do function arguments invoke a function?

In Java, when a method is called, the methods arguments invoke the method. Do functions in C do something similar?

Chad

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#71795

On 10/4/2015 5:15 AM, Chad wrote:
> In Java, when a method is called, the methods arguments invoke the method. Do functions in C do something similar?

     The arguments don't invoke the method or function, the call
operator invokes it.  In both Java and C, the call operator is
written as a parenthesized list (possibly empty) of argument
expressions, immediately following a method reference (Java) or
function pointer expression (C).

	func ()
	^^^^ ^^
	|     call operator (no arguments)
	|
	function pointer


	gunc (a, b, c)
	^^^^ ^^^^^^^^^
	|    call operator (three arguments)
	|
	function pointer

     (The term "call operator" is my own invention, as the Standard
doesn't actually refer to such an operator: It just says, in 6.5.2.2,
that the construct "is a function call."  On the other hand, the
containing section 6.5.2 is titled "Postfix operators," so speaking
of a "function call operator" isn't entirely off-the-call, er, -wall.)

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#71849

The phrase "arguments invoke the function" is take directly from the Introduction to Java Programming by Y. Daniel Ling.

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#71853

On 10/4/2015 4:52 PM, Chad wrote:
> The phrase "arguments invoke the function" is take directly from the Introduction to Java Programming by Y. Daniel Ling.

     She's wrong, or she's not writing about what you think she is,
or she's been taken out of context.  (Also, "function" is a strange
word to find in a Java text; Java has "methods.")

     In both Java and C, consider the function or method call

	yodel()

There are no arguments at all, yet the method or function is invoked
anyhow.  If the arguments were the invokers, how could invocation
occur in the absence of arguments?

     Perhaps she wrote that the argument *list* invokes the function,
and that would be about as reasonable as my "call operator" phrase,
and as sloppy.  But the arguments themselves?  I can't find much
enthusiasm for that wording, as it seems to me misleading.

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#71854

On 10/04/2015 04:52 PM, Chad wrote:
> The phrase "arguments invoke the function" is take directly from the Introduction to Java Programming by Y. Daniel Ling.


Could you give us the full context in which that phrase is used? It
doesn't seem to make sense, but a better understanding of the context
might change that.

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#71904

On Sun, 4 Oct 2015 13:52:32 -0700 (PDT), Chad <cdalten@gmail.com>
wrote:

>The phrase "arguments invoke the function" is take directly from the Introduction to Java Programming by Y. Daniel Ling.

I think you have misunderstood something he wrote in explaining method
overloading. It would be nice if you could cite where the quotation
appears in his book and to which edition you are referring.

Java has classes, classes have methods, methods can be overloaded.
This means two methods of a class can have the same name but take
different number or types of arguments. The particular method to be
called must be called according to the type or number of their
arguments.

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#71905

On Sun, 4 Oct 2015 13:52:32 -0700 (PDT), Chad <cdalten@gmail.com>
wrote:

>Y. Daniel Ling

His name is Y. Daniel Liang.

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#71920

Section 5.5, near the bottom of page 163

"Listing 5.5 gives another program that demonstrates the effect of passing by value. The program creates a method for swapping two variables. The swap method is invoked by passing two arguments."

And in section 11.7, near the middle of page 385

"Method displayObject (line 10) takes a parameter of the GeometricObject  type. You can invoke displayObject by passing an instance if GeometricObject (e.g, new Circle4(1, "red", false) and new Rectangle(1, 1, "black", false) in lines 5-6)."

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#71930

On 10/04/2015 10:50 PM, Chad wrote:
> Section 5.5, near the bottom of page 163
> 
> "Listing 5.5 gives another program that demonstrates the effect of
> passing by value. The program creates a method for swapping two
> variables. The swap method is invoked by passing two arguments."

Note: the swap method is not invoked by the two arguments, it is invoked
by passing two arguments. What passes those two arguments? The code that
calls the method. That code is itself part of some other method, so it
is the calling method that does the passing, and it is therefore also
the calling method that invokes the called method.

> And in section 11.7, near the middle of page 385
> 
> "Method displayObject (line 10) takes a parameter of the
> GeometricObject  type. You can invoke displayObject by passing an
> instance if GeometricObject (e.g, new Circle4(1, "red", false) and
> new Rectangle(1, 1, "black", false) in lines 5-6)."

Again, it is the passing of arguments that invokes the method, and not
the arguments themselves.

Getting back to your original question, corrected to reflect this
distinction: yes, in C, functions which take arguments (not all of them
do) can be invoked by passing such arguments to the called function.
A function that takes no arguments can be invoked by passing it no
arguments. I presume the same is true in Java?
-- 
James Kuyper

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#71824

On 10/04/2015 05:15 AM, Chad wrote:
> In Java, when a method is called, the methods arguments invoke the method. Do functions in C do something similar?

Could you explain what that phrase "the method's arguments invoke the
method" means to you? Knowing that, I might be able to answer with
respect to C. As it stands, the phrase doesn't make sense to me.

"arguments" are not actors, they are things that are acted on, so they
can't, in themselves, invoke anything. Because of my experience, I tend
to associate the term "method" with the C++ concept of a class member
function - if the term has a significantly different meaning for Java,
you should explain that meaning. C++ member functions are actors, and
one of the actions they can perform is to call (invoke) another member
function associated with the same object, or one associated with any
other object that they have access to, and they can pass arguments to
that other method. Possibly this understanding is C++-specific, and
there's something in Java that makes it meaningful to talk about an
argument invoking something. But if so, you'll have to explain that
meaning, before I can answer your question.

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#71834

On 10/04/2015 01:19 PM, Stefan Ram wrote:
> Newsgroups: comp.lang.c,comp.lang.java.programmer
> 
> James Kuyper <jameskuyper@verizon.net> writes:
>> On 10/04/2015 05:15 AM, Chad wrote:
> 
>>> In Java, when a method is called, the methods arguments invoke the method.
>      ^^^^ thus the Newsgroups header!
> 
>> Could you explain what that phrase "the method's arguments invoke the
>> method" means to you? Knowing that, I might be able to answer with
>> respect to C. As it stands, the phrase doesn't make sense to me.
> 
>   You are right!
> 
>   To »invoke« means to start, to execute, to run something. Arguments are
>   expressions that can be part of a method invocation expression.

OK - it's just as true in C/C++ that the argument of a function can be
the result of evaluating an expression. I hadn't thought of his question
in those terms. In that sense, in C++ an argument expression can invoke
methods associated with the objects involved in the expression, and can
invoke methods associated with the same class that the calling method is
associated with, even including another instance of the same method.
However, they cannot be said, in any sense, to invoke the same instance
of that method which they themselves are arguments of. It's the calling
code that does that invocation, not the arguments.

Evaluation of all method arguments must be complete, before evaluation
of the method itself can start, so it's never the case that the
arguments themselves invoke the instance of the method that they
themselves are arguments to. Does Java have different rules in this
regard that would make Chad's comment meaningful?

>  For example, in Java, the following is an expression:
> 
> java.lang.Math.random()
> 
>   . This method invocation expression (JLS 15.12) has no arguments.
>   If the method's arguments would invoke the method, it would not
>   be invoked here, since there are no arguments.
> 
>   Moreover, a method does not have arguments in Java at all. It has
>   /parameters/. A /method invocation expression/ has arguments.

That distinction applies to C/C++ as well.

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#71828

Le 04/10/2015 11:15, Chad a écrit :
> In Java, when a method is called, the methods arguments invoke the method. Do functions in C do something similar?
>
> Chad
>

In C, if you call sin(x) the "sin" generic function will resolve into 
different functions: sinl() if x is long double, or csin, if x is a 
complex number. This is defined in the standard header <tgmath.h>.

In the lcc-win compiler you can mark functions as "overloaded", i.e. it 
consists of a table of several functions that are called according to 
the set of arguments of the call, the "signature".

For instance you can write programs that are indepenent of the specific 
type of number they are dealing with, making possible to have several 
versions of the same code with a single source. Or you can abstract 
certain actions with abstract interfaces that are valid for a set of 
slightly different types.

In C++ all functions are actually "overloaded", in the lcc-win 
implementation only those explicitely marked so. And since no function 
is overloaded by default you can still have error messages from the 
compiler when you make a call with the wrong arguments. Not from the 
linker complaining because of a missing overload.

But I am biased of course.

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#71878

Chad <cdalten@gmail.com> writes:
> In Java, when a method is called, the methods arguments invoke the
> method. Do functions in C do something similar?

As others have suggested, that statement about Java doesn't seem to make
sense.

The Java Language Specification describes run-time method invocation as
a 5-step process.  Evaluating the arguments is step 2; transferring
control is step 5.

I'm no expert on Java, so perhaps I'm missing something.  In any case,
it doesn't make sense in C.

A C function call evalautes the prefix (which is usually just a funciton
name), evaluates the arguments, and invokes the function.  Invoking the
function assigns the argument values to the parameters before the body
of the function starts executing.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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#71926

On Sun, 4 Oct 2015 02:15:03 -0700 (PDT), Chad wrote:

>In Java, when a method is called, 
>the methods arguments invoke the method. 
>Do functions in C do something similar?

no in C there is not overload as C++ and Java [i presume]
for invoke one function is significative only the name not the args

>Chad

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