Converting a large floating-point number to a single-line string

Question

When I feed a large (or small) enough floating-point number to ToString, it produces a two-line string, with the first line containing only the exponent of 10:

In := ToString[12345.^6]
Out :=           24
       3.53954 10

This creates problems because it's very counterintuitive when written to a log file. For example ToString[{51.5^7, 2, 3, 12345.^6}] would be written out as

           11                  24\n{9.60839 10  , 2, 3, 3.53954 10  }

which is practically unrecognizable for what it is, especially when inserted in the middle of other output. I would like to see output like

{9.60839E+11, 2, 3, 3.53954E+24}

or, if not that, I'd be fine with something like

{9.60839*^11, 2, 3, 3.53954*^24}

What can I do to print out floating-point numbers in a format suitable for single-line output?

Answer 1

Admittedly hackish, but you could use

numbers = RandomReal[10^10, 3]

ToString[ToString[#, CForm] & /@ numbers]

or

ToString[ToString[#, FortranForm] & /@ numbers]

It gives

{3.672422352722051e9, 8.491123505444411e9, 1.7587409493599138e9} 

Mathematica usually likes to wrap long lines. This won't happen here because by default ToString uses PageWidth -> Infinity

Answer 2

There is already a built in function to handle this — it's called ScientificForm. You can get the output you desire as:

ScientificForm[12345.^6, NumberFormat -> (#1 <> "E" <> #3 &)] // ToString
Out[1]= 3.53954E24

StringForm only affects the display, so to export it correctly as a string to a log file, you'll have to wrap it in ToString like I've done. If you're only going to display it, you can drop that.

Answer 3

Just ask for it in InputForm:

In[1]:= ToString[12345.^6, InputForm]

Out[1]= 3.539537889086625*^24