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| author | Fuwn <[email protected]> | 2024-04-07 23:18:32 -0700 |
|---|---|---|
| committer | Fuwn <[email protected]> | 2024-04-07 23:18:32 -0700 |
| commit | c1b6ffe70bd281c6c230fd63fabcaac2aff47514 (patch) | |
| tree | e8af3b1782a7cd0754590ed618fddc1bdb9b7385 /chapter4/dynademo.cxx | |
| download | dscode-main.tar.xz dscode-main.zip | |
Diffstat (limited to 'chapter4/dynademo.cxx')
| -rw-r--r-- | chapter4/dynademo.cxx | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/chapter4/dynademo.cxx b/chapter4/dynademo.cxx new file mode 100644 index 0000000..fa10473 --- /dev/null +++ b/chapter4/dynademo.cxx @@ -0,0 +1,102 @@ +// FILE: dynademo.cxx
+// This is a small demonstration program showing how a dynamic array is used.
+#include <iostream> // Provides cout and cin
+#include <cstdlib> // Provides EXIT_SUCCESS and size_t
+#include <cassert> // Provides assert
+using namespace std;
+
+// PROTOTYPES for functions used by this demonstration program
+void allocate_doubles(double*& p, size_t& n);
+// Postcondition: The user has been prompted for a size n, and this size has been read.
+// The pointer p has been set to point to a new dynamic array containing n doubles.
+// NOTE: If there is insufficient dynamic memory, then bad_alloc is thrown.
+
+void fill_array(double data[ ], size_t n);
+// Precondition: data is an array with at least n components.
+// Postcondition: The user has been prompted to type n doubles, and these
+// numbers have been read and placed in the first n components of the array.
+
+double average(const double data[ ], size_t n);
+// Precondition: data is an array with at least n components, and n > 0.
+// Postcondition: The value returned is the average of data[0]..data[n-1].
+
+void compare(const double data[ ], size_t n, double value);
+// Precondition: data is an array with at least n components.
+// Postcondition: The values data[0]..data[n-1] have been printed with a
+// message saying whether they are above, below, or equal to value.
+
+
+int main( )
+{
+ double *numbers; // Will point to the first component of an array
+ size_t array_size;
+ double mean_value;
+
+ // Allocate an array of doubles to hold the user�s input.
+ cout << "This program will compute the average of some numbers. The\n";
+ cout << "numbers will be stored in an array of doubles that I allocate.\n";
+ allocate_doubles(numbers, array_size);
+
+ // Read the user�s input and compute the average.
+ fill_array(numbers, array_size);
+ mean_value = average(numbers, array_size);
+
+ // Print the output.
+ cout << "The average is: " << mean_value << endl;
+ compare(numbers, array_size, mean_value);
+ cout << "This was a mean program.";
+
+ return EXIT_SUCCESS;
+}
+
+void allocate_doubles(double*& p, size_t& n)
+// Library facilities used: iostream.h, stdlib.h
+{
+ cout << "How many doubles should I allocate?" << endl;
+ cout << "Please type a positive integer answer: ";
+ cin >> n;
+ p = new double[n];
+}
+
+void fill_array(double data[ ], size_t n)
+// Library facilities used: cstdlib
+{
+ size_t i;
+ cout << "Please type " << n << " double numbers: " << endl;
+
+ // Read the n numbers one at a time.
+ for (i = 0; i < n; ++i)
+ cin >> data[i];
+}
+
+void compare(const double data[ ], size_t n, double value)
+{
+ size_t i;
+
+ for (i = 0; i < n; ++i)
+ {
+ cout << data[i];
+ if (data[i] < value)
+ cout << " is less than ";
+ else if (data[i] > value)
+ cout << " is more than ";
+ else
+ cout << " is equal to ";
+ cout << value << endl;
+ }
+}
+
+double average(const double data[ ], size_t n)
+// Library facilities used: cassert, cstdlib
+{
+ size_t i; // An array index
+ double sum; // The sum of data[0] through data[n - 1]
+
+ assert(n > 0);
+
+ // Add up the n numbers and return the average.
+ sum = 0;
+ for (i = 0; i < n; ++i)
+ sum += data[i];
+ return (sum/n);
+}
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