Output formatting

Question

Is it possible to format a mathematica output in a way that all the fractional numbers are written first followed by other constants or functions?

Example:

output= 12/7*x + 120/17*x*y 

or

output= (12*x)/7 + 120/17*x*y

which when saved in a file becomes

(12*x)/7 + (120*x*y)/17

However I was asking if the output can be formatted in the following form

12/7*x + 120/17*x*y

PS. I am wring the expression as a .m extension and running this file through a terminal. I am not using notebook .nb interface.

Answer 1

Sounds like you want to control the OutputForm of an expression. In that case, you could do something like:

Unprotect[Times];
Format[r_Rational t_, OutputForm] := SequenceForm[r] SequenceForm[t]
Protect[Times];

For example:

12/7*x + 120/17*x*y //OutputForm

12     120
-- x + --- x y
7      17

Update

From the comments, it seems you want to control the formatting when using Put. Since Put uses InputForm when writing to a file, you need to modify InputForm instead. So:

Unprotect[Times];
Format[r_Rational t_, InputForm] := SequenceForm[r] SequenceForm[t]
Protect[Times];

Example:

(12/7*x + 120/17*x*y) >> output.dat;
Import["output.dat", "String"]

"12/7*x + 120/17*x*y "

Answer 2

Does something like this give you what you want?

12/7*x + 120/17*x*y // TraditionalForm

If it is, then I would recommend changing your preferences to default to traditional form for all output. I personally quite like the style of traditional form. This can be found in the preferences manager under Cell Options >> New Cell Defaults >> CommonDefaultFormatTypes and change from whatever it currently says to the right of "Output" to be "TraditionalForm" (no quotes).