i:(0:"i/18")^'" "
+/{.")"/"."\"("/")"\"."/"("\|x}'i

paren:{s:-2_x="(";e:2_x=")";p:&0+s&e;x@(!#x)^p,p+2} / (x) -> x
op:{ / +: x+y -> z; *: [^+]x*y[^+] -> z
 b:|/"()"=\:x
 p:x=" +"y~"*"
 k:-1+&0+~|/(~x=y;-2_0,0,p;2_p,0,0;1_b,0;-1_0,b)
 x{[op;x;y],/(y#x;0+"0"+op/(x(y;y+2))-"0";3_y_x)}[.y]/|k}
+//-"0"-{paren@op[;"*"]op[;"+"]x}/'i