BABAR C++ Course Running the Examples - HEPHY

ArraysExample Code and a TestA collection of elements of same typefloat x[100]; // like REAL*4 X(100) in F7• first element of array is x[0]• last element of array is x[99]Initializing array elementsfloat x[3] = {1.1, 2.2, 3.3};float y[] = {1.1, 2.2, 3.3, 4.4};• can let the compiler calculate the dimensionMulti-dimensions arraysfloat m[4][4]; // like REAL*4 M(4,4) in F7int m [2][3] = { {1,2,3}{4,5,6} };• elements appear row-wise• Fortran elements appear column-wise• Thus m[0][1] in C/C++ is M(2,1) in FortranMultiplying matrices (ch2/mat3by3.C)float m[3][3], m1[3][3], m2[3][3];// Code that initializes m1 and m2 ...// m = m1 * m2double sum;for (int i = 0; i < 3; i++) {for (int j = 0; j < 3; j++) {sum = 0.0;for (int k = 0; k < 3; k++) {sum += m1[i][k] * m2[k][j];}m[i][j] = sum;}}• If you understand this code, then you know enoughC/C++ to code the algorithmic part of your code• At the beginning of this session, the above codewould probably have been gibberish• If you can not understand this code, then I’m goingtoo fast :-(• royal pain to interface C/C++ with FortranBABAR C++ Course 29 Paul F. KunzBABAR C++ Course 30 Paul F. Kunz