
---- Read the text file "particle_events.txt" ----

The file contains a sequence of events, and for each event:
- an integer identifier,
- the 3 decay point coordinates
- the number of particles,
- for each particle the electric charge and the 3 momentum components
The file is written in text format, not binary (different from the Bragg
example!).

***
Create a function "read" taking as arguments:
- the reference to an input file stream,
- the reference to 3 floats to fill with the decay point coordinates,
- an array of integers to fill with electric charges,
- 3 arrays of float to fill with momenta components
and returning the number of particles.

***
Create a function "dump" taking as argument:
- the number of the event, 
- the number of particles,
- 3 floats for the decay point coordinates,
- an array of integers containing electric charges,
- 3 arrays of float containing momenta components
and printing a dump on the screen.
Write on the screen only the numbers, do not add any text as "Event number:"
or "these are the particles:"; the output should be usable as input for
a following run of the program.

***
Create a "main" function taking the file name from the command string, 
opening the file and calling the read and dump functions.
Dimension the arrays in the "main", using 10 as max number of particles. 
For each event try to read the event identifier in the "main", and on 
success call the "read" function to read the other data and then call 
the "dump" function.

********* final list of functions *********

main                   to do
read                   to do
dump                   to do
