Is flex-lexer a performant(fast) converter for simple regex recognition and replacement?

Question

I'm working on a project for my university, requiring to go though decently large files (>50MB), and i used flex to basically rewrite a file composed of line such as

1 1:41 3:54 7:40 13:8

2 4:7 7:8 23:85

into

1 1 3 7 13

2 4 7 23

(basically, turning the

number_a:number_b

into

number_a

, and printing the output in a file at execution)

My question is, since i'm writing the rest of my program in C++ : was that a good reflex since flex is supposed to be fast (the

f

in flex standing for fast), or am I just wrong and there's much simpler and still efficient way to do that in C++ ?

I'm pretty new to C++, so I have a lot of C coding reflexes and little knowledge of all the tools available, and of their performance.

Here is the piece of code i wrote in flex :

%{

#include<stdio.h> 

unsigned int nb_doc = 1;//prend en compte le premier doc

unsigned int i;

%}

couple_entiers      [0-9]+:[0-9]+

retour_chariot      \n[0-9]+

autre               .

%%

{couple_entiers}      {i=0;

                       while(yytext[i] != ':'){

                            printf("%c",yytext[i]);

                            i++;

                         }

                      }

{retour_chariot}      {nb_doc ++; printf("%s",yytext);}

{autre}               {printf("%s",yytext);}



%%

int main (void){

    yylex();

    printf("\n\n%d",nb_doc);

    return 0;

}

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Answer 1

Consider replacing your custom code with a general solution:

system("sed -E 's/:\d+ / /g'");

:)

Is flex-lexer a performant(fast) converter for simple regex recognition and replacement?

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