C语言实现“计算器”

 

支持 加减乘除 混合运算。具体设计见代码。 

 

#include <assert.h>

#include <stdio.h>

 

///////////////////////////////////////////////////////////////////////////////

 

typedef char bool;

#define true 1

#define false 0

 

typedef struct {

        const char *szExp;

  int nPos;

} Context;

 

typedef struct{

        int nVal;

  Context tCon;

} Env;

 

typedef bool (*ExpectOperation)(Context *pCon);

typedef int (*GetCalcValue)(Env *pEnv);

int MixCalc(Env *pEnv);

 

///////////////////////////////////////////////////////////////////////////////

 

int GetValue(Env *pEnv)

{

int nVal = 0;

        const char *szExp = pEnv->tCon.szExp;

int nPos = pEnv->tCon.nPos;

if (*(szExp+nPos) == '(')

{

                pEnv->tCon.nPos ++;

nVal = MixCalc(pEnv);

                pEnv->tCon.nPos ++;

}

else

{

while ((*(szExp+nPos) >= '0')

&& (*(szExp+nPos) <= '9'))

{

nVal = nVal*10 + (*(szExp+nPos) - '0');

nPos ++;

}

        pEnv->tCon.nPos = nPos;

}

return nVal;

}

 

bool IsAddSubOperation(Context *pCon)

{

    return (pCon->szExp[pCon->nPos] == '+') || (pCon->szExp[pCon->nPos] == '-');

}

bool IsMulDivOperation(Context *pCon)

{

    return (pCon->szExp[pCon->nPos] == '*') || (pCon->szExp[pCon->nPos] == '/');

}

 

char GetOperation(Context *pCon)

{

char cOperation = '\0';

char cCurrChar = pCon->szExp[pCon->nPos];

if ((cCurrChar == '+')

|| (cCurrChar == '-')

         || (cCurrChar == '*')

|| (cCurrChar == '/'))

{

cOperation = cCurrChar;

pCon->nPos ++;

}

return cOperation;

}

 

int ApplyOperation(int nVal1, int nVal2, char cOperation)

{

switch (cOperation)

{

case '+':

return nVal1 + nVal2;

case '-':

return nVal1 - nVal2;

case '*':

return nVal1 * nVal2;

case '/':

return nVal1 / nVal2;

}

return 0;

}

 

int Calc(Env *pEnv, ExpectOperation fExpOperation, GetCalcValue fGetCalcValue)

{

        int nVal1 = fGetCalcValue(pEnv);

int nVal2 = 0;

char cOperation;

while (fExpOperation(&pEnv->tCon))

{

                cOperation = GetOperation(&pEnv->tCon);

                nVal2 = fGetCalcValue(pEnv);

nVal1 = ApplyOperation(nVal1, nVal2, cOperation);

}

pEnv->nVal = nVal1;

return nVal1;

}

 

int Mul_Div(Env *pEnv)

{

return Calc(pEnv, IsMulDivOperation, GetValue);

}

 

int MixCalc(Env *pEnv)

{

    return Calc(pEnv, IsAddSubOperation, Mul_Div);

}

 

///////////////////////////////////////////////////////////////////////////////

 

int main()

{

        Env env1 = {0, "1+2", 0};

Env env2 = {0, "1+2-3+4+5", 0};

Env env3 = {0, "1*2", 0};

Env env4 = {0, "1*2*3*4/2", 0};

Env env5 = {0, "1*2+2*4", 0};

Env env6 = {0, "1*(2+2)*4+3", 0};

 

MixCalc(&env1);

assert(env1.nVal == 3);

assert(env1.tCon.nPos == 3);

MixCalc(&env2);

assert(env2.nVal == 9);

assert(env2.tCon.nPos == 9);

 

Mul_Div(&env3);

assert(env3.nVal == 2);

assert(env3.tCon.nPos == 3);

Mul_Div(&env4);

assert(env4.nVal == 12);

assert(env4.tCon.nPos == 9);

 

MixCalc(&env5);

assert(env5.nVal == 10);

assert(env5.tCon.nPos == 7);

MixCalc(&env6);

assert(env6.nVal == 19);

assert(env6.tCon.nPos == 11);

 

printf("Try Calculate. \n");

return 0;

}