62 lines
1.5 KiB
C++
62 lines
1.5 KiB
C++
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#include <iostream>
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#include <cstdlib>
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#include <cstring>
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#include "calc.hh"
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static int pos = 0;
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void calc_reset(){
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pos = 0;
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}
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int calc_factor_value(const char * factor){
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int result = 0;
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char c = factor[pos];
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if( c == '('){ // if expression has '(', calculate the expression in the '()'
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pos++;
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result = calc_expression_value(factor);
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pos++;
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}else{
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while(isdigit(c)){ // Get the number to calculate
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result = 10 * result + c - '0';
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pos++;
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c = factor[pos];
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}
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}
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return result;
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}
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int calc_term_value(const char * term){
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int result = calc_factor_value(term); // Get the first number
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while(true){
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//pos++; // Calc the multiplication and divide
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char op = term[pos];
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if(op == '*' || op == '/'){
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pos++;
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int value = calc_factor_value(term); // Get another value
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if(op == '*') result *= value;
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else result /= value;
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}else{
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break;
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}
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}
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return result;
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}
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int calc_expression_value(const char * expression){
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int result = calc_term_value(expression); // Calc the result of expression
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//bool more = true;
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while(true){
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char op = expression[pos];
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if(op == '+' || op == '-'){ // Calculate for add and subb
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pos++;
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int value = calc_term_value(expression);
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if( op == '+') result += value;
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else result -= value;
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}else{
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break;
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}
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}
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return result;
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}
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