On 6 March 2015 at 17:21, Nicol Bolas wrote:
> Explain to me, the novice C++ programmer, why this thing which doesn't look
> like a template suddenly became a template. Explain to me why I have to
> implement it in a header, even though it looks exactly like every other
> non-template function declaration/definition.
>
> To the novice C++ programmer, it isn't "all just programming." Whether
> something is a template matters.

Ah, the "won't somebody think of the children" argument.

The answer to why it suddenly became a template is that its parameter
is a concept, not a type. A concept is a family of types.  I don't see
why that should be much harder to teach than "a function template is a
family of functions" and "a class template is a family of types".

If we're teaching novices how to write C++ templates based on "just
put template<blah> before it and make sure it's in a header" that
doesn't seem like a very sound basis for learning anything more than
arbitrary syntactic rules and cargo cult programming.

(Is it time to trim the CC list so this doesn't continue to be
cross-posted everywhere?)

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On Friday, March 6, 2015 at 12:38:14 PM UTC-5, Jonathan Wakely wrote:
>
> On 6 March 2015 at 17:21, Nicol Bolas wrote:
> > Explain to me, the novice C++ programmer, why this thing which doesn't
> look
> > like a template suddenly became a template. Explain to me why I have to
> > implement it in a header, even though it looks exactly like every other
> > non-template function declaration/definition.
> >
> > To the novice C++ programmer, it isn't "all just programming." Whether
> > something is a template matters.
>
> Ah, the "won't somebody think of the children" argument.
>
> The answer to why it suddenly became a template is that its parameter
> is a concept, not a type. A concept is a family of types.  I don't see
> why that should be much harder to teach than "a function template is a
> family of functions" and "a class template is a family of types".
>

If a "family of functions" is so fundamentally different from a regular
function that it can't be declared/defined in the same way, why does it
look exactly like a regular function? If swapping one identifier for
another can so radically change how you go about implementing something,
shouldn't it be more syntactically obvious that you've made a major change?

Without the template keyword, it doesn't look like a template. And
therefore, it is not immediately obvious that it should be treated as such.

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<div dir=3D"ltr"><br><br>On Friday, March 6, 2015 at 12:38:14 PM UTC-5, Jon=
athan Wakely wrote:<blockquote class=3D"gmail_quote" style=3D"margin: 0;mar=
gin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">On 6 March =
2015 at 17:21, Nicol Bolas wrote:
<br>&gt; Explain to me, the novice C++ programmer, why this thing which doe=
sn't look
<br>&gt; like a template suddenly became a template. Explain to me why I ha=
ve to
<br>&gt; implement it in a header, even though it looks exactly like every =
other
<br>&gt; non-template function declaration/definition.
<br>&gt;
<br>&gt; To the novice C++ programmer, it isn't "all just programming." Whe=
ther
<br>&gt; something is a template matters.
<br>
<br>Ah, the "won't somebody think of the children" argument.
<br>
<br>The answer to why it suddenly became a template is that its parameter
<br>is a concept, not a type. A concept is a family of types. &nbsp;I don't=
 see
<br>why that should be much harder to teach than "a function template is a
<br>family of functions" and "a class template is a family of types".
<br></blockquote><div><br>If a "family of functions" is so fundamentally di=
fferent from a regular function that it can't be declared/defined in the sa=
me way, why does it look exactly like a regular function? If swapping one i=
dentifier for another can so radically change how you go about implementing=
 something, shouldn't it be more syntactically obvious that you've made a m=
ajor change?<br><br>Without the template keyword, it doesn't look like a te=
mplate. And therefore, it is not immediately obvious that it should be trea=
ted as such.</div><br></div>

<p></p>

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