procedure form(arg1,op,arg2)
arg1 := fix(arg1)
arg2 := fix(arg2)
return case op of {
"+" : add(arg1,arg2)
"-" : sub(arg1,arg2)
"*" : mpy(arg1,arg2)
"/" : div(arg1,arg2)
"~" : drv(arg1,arg2)
default : symop(arg1,op,arg2)
}
end