Can I use my longspear to attack at both 10 feet and 5 feet? I know that the rules for reach weapons don't allow them to attack adjacent foes, but can I use the improvised weapon rules to say that the blunt end of my longspear resembles a club and use it to attack adjacent foes? I know that the improvised weapon rules say they are for objects not designed to be weapons, but the blunt end of my longspear was not designed to be a weapon, right?
You could choose to wield your longspear as an improvised blunt weapon. In this case, it threatens only your adjacent squares, and not the further squares. If you are wielding it as a longspear, though, to threaten the further squares, then your grip precludes the use as an improvised blunt weapon. The rules are silent on how long it would take to shift between the two, but switching between a one-handed and a two-handed grip with a one-handed weapon like a longsword is a free action (and can thus be only taken on your turn), so it should take at least as long as that, thus preventing you from simultaneously threatening all of the squares at once. Incidentally, using the longspear as an improvised weapon in this way would not allow you to benefit from any magical enhancements it may possess, nor would you add benefits that apply when attacking with a longspear (such as Weapon Focus (longspear), but you would apply any benefits from using an improvised weapon (such as Catch Off-Guard).
这一条可以驳倒楼上关于酸蚀的解释。一个酸蚀长矛用作临时武器就不会有魔法增强了