Template within template: why "`' should be ` ' within a nested template argument list"

Question

I know that when we are using template inside another template, we should write it like this:

vector > s;

and if we write it without the whitespace:

vector> s;

we will get an error:

`>>' should be `> >' within a nested template argument list

I see this is understandable, but I just can't help but wondering, in which cases will this be really ambiguous?

user_2700586 · Answer

Stream Syntax

cin >> var;

Vs

Nested Template Syntax

For>

First phase of Compiler, lexical analyser will not be able to recognise.

Template within template: why "`>>' should be `> >' within a nested template argument list"