Go language stack implementation arithmetic expression

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The middle sequence expression is converted into a post-order expression, and the value is computed by the post -ordering expression .

Package main//expression//author:xiong Chuan liang//date:2015-2-2import ("FMT" "Github.com/xcltapestry/xclpkg/algorithm" " StrConv "" Errors ") func main () {//Ordinal expression post-order expression//A+b = ab+//(a+b)/c = ab+c///a+b* (c+d) = abcd+ *+//a*b+c* (D-E)/f = ab*cde-*f/+//str: = "a*b+c* (D-E)/F"//str: = "1*2+3* (4-5)/6" str: = "1*2+3* (5-1)/2" Exp,err: = Expconve RT (STR) If err! = Nil {fmt. Println ("The middle order expression fails!", err)}else{exp (EXP)}//v: = 1*2+3* (4-5)/6v: = 1*2+3* (5-1)/2fmt. PRINTLN ("Standard result:", v)}func Expconvert (str string) (String,error) {var result stringstack: = algorithm. Newstack () for _,s: = range str {ch: = string (s) if Isoperator (CH) {//Is the operator if stack. Empty () | | ch = = "(" {stack. Push (ch)}else{if ch = = ")" {//processing brackets for{if stack. Empty () {return "", errors. New ("There is a problem with the expression!" The corresponding \ "(\" number ")}if stack was not found. Top (). (string) = = "(" {break}result + = stack. Top (). (string) stack. Pop ()}//pops Up "(" stack. Top () stack. Pop ()}else{//non-bracket//Comparison priority for{if stack. Empty () {break} m: = Stack. Top (). (string) if priority (CH) > PrioriTy (m) {break} result + = M stack. Pop ()} stack. Push (CH)}}}else{//non-operator result + = ch}//end isoperator ()}//end for range strfor {if stack. Empty () {break}result + = stack. Top (). (string) stack. Pop ()}fmt. Println ("Expconvert () str =", str) FMT. Println ("expconvert () result =", result) return Result,nil}func Exp (str string) {FMT. Println ("\ncalc \nexp ():", str) stack: = algorithm. Newstack () for _,s: = range str {ch: = string (s) if Isoperator (CH) {//Is the operator if stack. Empty () {break}b: = stack. Top (). (string) stack. Pop () A: = Stack. Top (). (string) stack. Pop () Ia,ib: = ConvToInt32 (A, b) SV: = FMT. Sprintf ("%d", Calc (Ch,ia,ib)) stack. Push (SV) fmt. Println ("Exp ()", A, "", CH, "", B, "=", SV)}else{stack. Push (CH) fmt. Println ("Exp () ch:", ch)}//end isoperator}//stack. Print () if!stack. Empty () {fmt. Println ("Expression operation result:", stack.) Top ()) stack. Pop ()}}func ConvToInt32 (A, B string) (Int32,int32) {ia, Erra: = StrConv. Parseint (A, ten, +) if Erra! = nil {panic (Erra)}ib, ERRB: = StrConv. parseint (b, ten, +) if ERRB! = nil {Panic (ERRB)}return Int32 (IA), Int32 (IB)}func isoperator (OP string) (bool) {switch (OP) {case "(", ")", "+", "-", "*", "/": Return Truedefault:return False}}func Priority (OP string) (int) {switch (OP) {case "*", "/": Return 3case "+", "-": Return 2case "(": return 1default:return 0}}func Calc (Op string,a,b Int32) (Int32) {switch (OP) {case ' * ': return (A * b) case "/": Return (A/b) c ASE "+": return (A + B) case "-": Return (a) Default:return 0}}

Result of Operation:

Expconvert () str    =  1*2+3* (5-1)/2expconvert () result =  12*351-*2/+calcexp (): 12*351-*2/+exp () Ch:  1EXP () Ch:  2Exp ()  1  *  2 = 2EXP () Ch:  3Exp () Ch:  5Exp () Ch:  1Exp ()  5  -  1 = 4EXP ()  3  *  4 = 12EXP () Ch:  2Exp ()  /  2 = 6EXP ()  2  +  6 = 8 expression operation Result:  8 Standard results:  8

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