GSoC 2016: Correct real write bug

[ghost]

This pull request tries to correct the bug noticed in #2148. It will switch to an exponential notation if the standard precision isn't enough to print the decimal part of the number.

Passed test/io and test/release on both linux64 and darwin with default settings.

[bradcray]

@mppf seems like the natural reviewer here, if he hasn't been made aware of this one already.

[ben-albrecht]

Hi @Panzone - nice work on this change.

I ran the full test suite for you and found the following errors:

 [Error matching program output for modules/standard/math/acosh]
 [Error matching program output for modules/standard/memory/countMemory/countMemory]
 [Error matching program output for types/scalar/bradc/piVals]
 [Error matching program output for types/scalar/bradc/piVals1a]
 [Error matching program output for types/scalar/bradc/piVals2]
 [Error matching program output for users/shetag/tensor]

I can send outputs if you're unable to reproduce them locally.

[mppf]

The code change itself looks good to me. Those failing tests probably just need .good updates but you'll need to double-check that the new output makes sense. Also, I'd like to see a new test that verifies some integers of different sizes print as expected (varying the number of digits in the integer).

[ghost]

Corrected the failing tests and added a new one.

[mppf]

Why does f print out with 1.00000e+05 and not 1+05 ? Can you get it to print the simpler version?

[mppf]

It looks good to me, other than the issue I noted. In particular, using the default format (e.g. with writeln) I don't expect it to print digits after the trailing zeros in exponential notation. Still, we're close...

[ghost]

It should now print the simpler version.

This code

var pi = 314159.2654;
writeln(pi);

pi = 100000.0;
writeln(pi);

pi = 100300.9;
writeln(pi);

now produces

3.14159e+05
1e+05
1.00301e+05

[mppf]

Passed full local testing.