How to join all lines till next condition?

Question

I can't find out how to join all lines till a next condition happens (a line with only 1 or more numbers) p.e.

input:

1    
text text text text (with numbers)   
text text text text (with numbers)    
2
this text   
text text text text (with numbers)  
text text text  
3  
text text text text (with numbers)  
4  
etc  

desidered output:

1 text text text text (with numbers) text text text text (with numbers)    
2 this text text text text text (with numbers) text text text  
3 text text text text (with numbers)  
4  
etc

I normally use global/^/,+2 join but the number of lines to join are not always 3 in my example above.

Answer 1

Instead of the static +2 end of the range for the :join command, just specify a search range for the next line that only contains a number (/^\d\+$/), and then join until the line before (-1):

:global/^/,/^\d\+$/-1 join

Answer 2

v/^\d\+/-j will do the trick.

v execute the function for each not matching the condition ^\d\+ your condition : Line starting with a number. -j go one line backward an join. Or if you prefer join the current line with the previous line.

So basically we join every lines not matching your condition with the previous line.