所谓命题演算公式是指由逻辑变量（其值为TRUE或FALSE）和逻辑运算符∧（AND）、∨（OR）和┐（NOT）按一定规则所组成的公式（蕴含之类的运算可以用∧、∨和┐来表示）。公式运算的先后顺序为┐、∧、∨，而括号（）可以改变优先次序。已知一个命题演算公式及各变量的值，要求设计一个程序来计算公式的真值。-The so-called propositional calculus formula refers to the logical variable (its value is TRUE or FALSE) and logical operators ∧ (AND), ∨ (OR) and ┐ (NOT) the formula for the composition according to certain rules (contains sort of operations can be used ∧, ∨ and ┐). The formula for computing the order for a ┐, ∧, ∨, and parentheses () can change the priorities. Given a propositional calculus formula and the value of a variable, to design a program to calculate the true value of the formula.