Because having been in industry several years is no reason not to redo an assignment I did as a sophomore in college.
grab input via libedit and output scan
remove extraneous neg rule in scanner
basic lexer complete

heads

default
browse log

clone

read-only
https://hg.sr.ht/~bmp/arithmetica
read/write
ssh://hg@hg.sr.ht/~bmp/arithmetica