0x1.5e-2     // invalid: hexadecimal mantissa requires p exponent
1_.5         // invalid: _ must separate successive digits
1._5         // invalid: _ must separate successive digits
1.5_e1       // invalid: _ must separate successive digits
1.5e_1       // invalid: _ must separate successive digits
1.5e1_       // invalid: _ must separate successive digits
</pre>


<h3 id="Imaginary_literals">Imaginary literals</h3>

Some compiler optimizations that would be valid in single-threaded programs are not valid in all Go programs.
In particular, a compiler must not introduce writes that do not exist in the original program,
it must not allow a single read to observe multiple values,
and it must not allow a single write to write multiple values.
</p>

<p>
All the following examples assume that `*p` and `*q` refer to

function contains no call instructions.
Otherwise, the local stack frame must not contain pointers,
and the assembly must confirm this fact by executing the
pseudo-instruction <code>NO_LOCAL_POINTERS</code>.
Because stack resizing is implemented by moving the stack,
the stack pointer may change during any function call:
even pointers to stack data must not be kept in local variables.
</p>

<p>

0x1.5e-2     // invalid: hexadecimal mantissa requires p exponent
1_.5         // invalid: _ must separate successive digits
1._5         // invalid: _ must separate successive digits
1.5_e1       // invalid: _ must separate successive digits
1.5e_1       // invalid: _ must separate successive digits
1.5e1_       // invalid: _ must separate successive digits
</pre>


<h3 id="Imaginary_literals">Imaginary literals</h3>