[PDF] C/C++ ROOT recent changes in the code. •

C/C++ROOTMatteoDuranti, Valerio Vagellimatteo.duranti@infn.it(cfr. https://www.tutorialspoint.com/cprogramming/c_file_io.htmhttps://www.tutorialspoint.com/c_standard_library/c_function_feof.htmhttp://www.cplusplus.com/doc/tutorial/files/https://www.tutorialspoint.com/cprogramming/c_preprocessors.htmhttp://www.cplusplus.com/articles/2LywvCM9/https://root.cern.ch/root/html534http://webhome.phy.duke.edu/~raw22/public/root.tutorial/basic_root_20100701.pdf)

C++•Programming language-Human "friendly" instructions (top level) that are translated to "machine" instructions by the compiler-Strict rules-Object Oriented•Structures interacting among themselves through methods

C++ Variables#include //# defines a preprocessorinstructionusing namespace std; //:: namespace resolutionoperatorintmain() { // { defines a scopeintx; //variable with type intis definedx=7+9; //variable x is initialized to some valuedouble d = 5.6; //variable d with type doubleis defined and initializedcout<

Algorithm Fluxif( this_expression== true ){ do_this(); }else{ do_that(); }•The flux of informaOon can be controlled by several construct•IF construct•decides which scope to solve, controlled by a boolean(true/false) valueintvalue=0;if( this_expression== true ){ value = this(); }else{ value = that(); }•Shortuct: if/else assignment in a lineintvalue = this_expression? this() : that();

Algorithm Flux•The flux of information can be controlled by several construct•FOR construct•Iterates the instructions in the scope for a fixed amount of timesfor( inti=0; i<100; i++){ do_this(); do_that();}•A FOR loop can be solved (exit the loop and continue with the code) with a breakcallfor( inti=0; i<100; i++){ boolI_am_bored= check_if_bored();if( I_am_bored) break; }•A continuecall allows to skip to the next iteration without solving the complete scopefor( inti=0; i<100; i++){ boolI_like_this= check_if_good(i);if( !I_like_this) { continue; }else { do_stuff_on_this(); }}

Algorithm Flux•The flux of information can be controlled by several construct•WHILE construct•Iterates the instructions in the scope while the heading expression is truewhile( head_expr==true ){do_this();if( time_to_stop() ) head_expr=false;}•breakcalls and continuecalls work as for the FOR loop case

Arrays•An arrayis a group of elements with the same type indexed by the same variable#include using namespace std; intmain() {intxx[5] = {1,-3,1,0,4};intyy[5];for(inti=0; i<5; i++){ yy[i] = xx[i]-xx[0]; }floatmm[4][7];for(intii=0; ii<4; ii++)for(intjj=0; jj<7; jj++){ mm[ii][jj] = some_value(ii,jj);}return 0;}•An array is NOT a dynamic structure. If you want an array with a dynamic size, you should use a std::vectorhttp://www.cplusplus.com/reference/vector/vector/

Functions•A functionis a segment of code (i.e. a set of instructions) that perform a single task•Functions can be called during the execution of the programs.•Functions may return a single value, a complex object, or nothing.•Use functions! Make your code modular. It helps when things don't work and you have to debug your code.type fun_name(type par1, type par2, ... type parn){//instructions here;}intmagnitude( float number ){if( number<=0 ) return 0;else return (int)log10(number);}void even( intnumber ){printf("%d is %s\n", number, number%2==0 ? "even" : "odd" );return;}intmain() {intx=102;even(x);printf("magnitude is %d\n", magnitude(x) );102 is evenmagnitude is 2

Functions•A functionis a segment of code (i.e. a set of instructions) that perform a single task•Functions can be called during the execution of the programs.•Functions may return a single value, a complex object, or nothing.•Use functions! Make your code modular. It helps when things don't work and you have to debug your code.intsum( intx1, intx2=4 ){x1 = x1+x2;return x1;}intmain() {intx=102;ints = sum( x, 10 );printf("x:%d s:%d\n", x, s);inty=8;printf("y:%d s:%d\n", x, sum( sum(y,2) ) );}x:102 s:112y:8 s:14

Functionsintsum( intx1, intx2=4 ){x1 = x1+x2;return x1;}102x102x1?copy by valuex2102x110x2112x110x2s = sum(x,10);?s102x112s112x110x2112x110x21)2)3)4)5)6)

C++ Pointers•For a C++ program, the memory of a computer is like a succession of memory cells, each one byte in size, and each with a unique address. -Data representations larger than one byte occupy memory cells that have consecutive address•Each cell can be easily located in the memory by means of its unique address•When a variable is declared, the memory needed to store its value is assigned a specific location in memory (its memory address)•it may be useful for a program to be able to obtain the address of a variable during runtime in order to access data cells that are at a certain position relative to it.•Pointersare variables storing integers (usually memory addresses of other variables)•Arrays are pointers!

C++ Pointers#include using namespace std; intmain() { // {intx = 16; int*px = NULL; //pointer to integerisdefinedand initializedpx= &x; //value of pxis set to the address "&" of xint**ppx= &(px); //pointer to pointercout<

C++ Pointers#include using namespace std; intmain() { // {intx = 16; int* px = NULL; //pointer to integerisdefinedand initializedpx= &x; //value of pxis set to the address "&" of xint** ppx= &(px); //pointer to pointercout<

C++ Pointers#include using namespace std; intmain() { // {intx = 16; int* px = NULL; //pointer to integerisdefinedand initializedpx= &x; //value of pxis set to the address "&" of xint** ppx= &(px); //pointer to pointercout<

C++ Pointers#include using namespace std; intmain() { // {intx = 16; int* px = NULL; //pointer to integerisdefinedand initializedpx= &x; //value of pxis set to the address "&" of xint** ppx= &(px); //pointer to pointercout<

C++ Pointers#include using namespace std; intmain() { // {intx = 16; int* px = NULL; //pointer to integerisdefinedand initializedpx= &x; //value of pxis set to the address "&" of xint** ppx= &(px); //pointer to pointercout<

C++ Pointers & Functions#include using namespace std;void increase(intx) { x++; }; //pass by valuevoid p_increase(int* px) { (*px)++; }; //pass by pointervoid r_increase(int& x) { x++; }; //pass by referenceintmain(){inti=0;increase(i); cout<

File writing/reading (C)

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