To answer your initial question and to provide a condensed explanation for the reason behind your compile problem.

From the point of view of the compiler, templates are not normal functions or classes. They are compiled on demand, meaning that the code of a template function is not compiled until an instantiation with specific template arguments is required. At that moment, when an instantiation is required, the compiler generates a function specifically for those arguments from the template.

When projects grow it is usual to split the code of a program in different source code files. In these cases, the interface and implementation are generally separated. Taking a library of functions as example, the interface generally consists of declarations of the prototypes of all the functions that can be called. These are generally declared in a "header file" with a .h extension, and the implementation (the definition of these functions) is in an independent file with c++ code.

Because templates are compiled when required, this forces a restriction for multi-file projects: the implementation (definition) of a template class or function must be in the same file as its declaration. That means that we cannot separate the interface in a separate header file, and that we must include both interface and implementation in any file that uses the templates.

Since no code is generated until a template is instantiated when required, compilers are prepared to allow the inclusion more than once of the same template file with both declarations and definitions in a project without generating linkage errors.

Thanks saige

Another truly interesting domain in which the brain confuses the literal and metaphorical is cleanliness. In a remarkable study, Chen-Bo Zhong of the University of Toronto and Katie Liljenquist of Northwestern University demonstrated how the brain has trouble distinguishing between being a dirty scoundrel and being in need of a bath. Volunteers were asked to recall either a moral or immoral act in their past. Afterward, as a token of appreciation, Zhong and Liljenquist offered the volunteers a choice between the gift of a pencil or of a package of antiseptic wipes. And the folks who had just wallowed in their ethical failures were more likely to go for the wipes. In the next study, volunteers were told to recall an immoral act of theirs. Afterward, subjects either did or did not have the opportunity to clean their hands. Those who were able to wash were less likely to respond to a request for help that the experimenters had set up that came shortly afterward. Apparently, Lady Macbeth and Pontius Pilate weren’t the only ones to metaphorically absolve their sins by washing their hands.

via This Is Your Brain on Metaphors – NYTimes.com.

I wish you all the in-box peace you have denied me these last few weeks. For all those who dislike hate and foul language, stop reading here, please.

via Michael Gross : An Open Letter to Ann Coulter.

Now, what I’m not showing here is the actual number of uniques.  And I won’t because I want to maintain the illusion that I have a wildly popular site.

When these cooperating processes get out of sync, we can experience déjà vu, the intense and often disconcerting feeling that a situation is familiar even though it has never happened before. This feeling can occur when a brand-new situation is very similar to other events stored in our memory. For example, a Texas airport may seem vaguely familiar to you even though you have never been to Texas. It is possible the airport is strikingly similar to a single event stored in memory—perhaps you recently saw the airport in a movie or magazine. It is also possible that many memories of visiting similar airports create the sensation that you have been to this one. Déjà vu is a stronger version of this kind of memory error.

via What is going on in the brain when we experience déjà vu?: Scientific American.

I like how realistic Arsenic looks.  I also like….