GVim VimScript: Changing Font Size Function 1

"make gvim able to adjust font size using key command
command! FontLarger call s:fontLarger()
function! s:fontLarger()
	"store current setting to var curfont
	let curfont=&guifont
	echo "current font is:" . curfont
	"split by " " and extract the fontsize
	let list=split(curfont," ")
	echo "list contents:" . list[0] . list[1]

	"get length of the list
	let listlen=len(list)
	echo "listlen" . listlen
	"
	let newfontsize=list[listlen-1]+1
	"preparation for while statement
	let indexi=0
	let indexj=listlen
	let newfont=""
	"construct newfont strings using while loop
	while indexi < listlen "loop (listlen)th times
		echo "in the while loop"
		echo "listlen:" listlen
		echo "indexi:" indexi
		echo "indexj:" indexj
		echo list[indexi]
		"newfont=newfont . list[indexi]
		"use conditional statement if
		if indexi == 0 "first time, no add \space
			let newfont=newfont . list[indexi]
		elseif indexi != 0
			if indexi < listlen-1
				let newfont=newfont . " " . list[indexi]
			"if list[indexi] is numerical value, increment 1
			elseif indexi == listlen-1
				let newfontsize=list[indexi]+1
				echo "newfontsize:" . newfontsize
				let newfont=newfont . " " . newfontsize
			endif
		endif
		"update indexes	
		let indexi=indexi+1 
		let indexj=indexj-1 
	endwhile
	"edit curfont and get font size
	echo "newfont is:" . newfont
	let &guifont=newfont
endfunction