From f01e0b9e316c2ceca8765503c652051f17c8cc05 Mon Sep 17 00:00:00 2001
From: Myles Busig <mdbusig@gmail.com>
Date: Wed, 30 Oct 2024 00:34:59 -0700
Subject: [PATCH] Add solution for problem 3

---
 include/p3.h |  7 +++++++
 input_p3.dat |  4 ++++
 src/main.c   |  6 ++++++
 src/p3.c     | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 include/p3.h
 create mode 100644 input_p3.dat
 create mode 100644 src/p3.c

diff --git a/include/p3.h b/include/p3.h
new file mode 100644
index 0000000..097e665
--- /dev/null
+++ b/include/p3.h
@@ -0,0 +1,7 @@
+#ifndef P3_H
+#define P3_H
+
+double sum_file(const char* filename);
+
+#endif
+
diff --git a/input_p3.dat b/input_p3.dat
new file mode 100644
index 0000000..1f301c5
--- /dev/null
+++ b/input_p3.dat
@@ -0,0 +1,4 @@
+1.0
+2.2
+3.0
+5.4
diff --git a/src/main.c b/src/main.c
index dbc268c..e80b917 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2,6 +2,7 @@
 
 #include "p1.h"
 #include "p2.h"
+#include "p3.h"
 
 int main(void) {
 	// Problem 1
@@ -21,6 +22,11 @@ int main(void) {
 
 	printf("Average: %.2lf, Min: %.2lf, Max: %.2lf\n", avg, min, max);
 
+	// Problem 3
+	double sum_of_file = sum_file("input_p3.dat");
+
+	printf("Sum of file: %.2lf\n", sum_of_file);
+
 	return 0;
 }
 
diff --git a/src/p3.c b/src/p3.c
new file mode 100644
index 0000000..3a62ad0
--- /dev/null
+++ b/src/p3.c
@@ -0,0 +1,48 @@
+#include "p3.h"
+
+#define _CRT_SECURE_NO_WARNINGS
+
+#include <stdio.h>
+
+double sum_file(const char* filename) {
+	FILE* infile = fopen(filename, "r");
+	
+	double sum = 0.0;
+	double value = 0.0;
+
+	// NOTE: Using feof may fail if you're not careful! For example, if the file
+	// being read from contains trailing whitespace characters, EOF may not
+	// be set until one additional read is performed. In this case, this would
+	// cause fscanf to attempt to read one additional value that does not exist.
+	// On Linux, this additional read is needed even if there is no trailing
+	// whitespace, although this may differ on other systems.
+	//
+	// As another example, if fscanf encounters an unexpected value, the position
+	// inside of the file will not be increased. Since we are attempting to read
+	// floating-point numbers, if we add an alphabetic character to the input file,
+	// fscanf will be stuck in an infinite loop trying to read invalid data and
+	// never progressing.
+	/*while (!feof(infile)) {
+		value = 0.0;
+		fscanf(infile, "%lf", &value);
+
+		// Try changing the input file and see what this prints!
+		printf("(feof) Adding value %.2lf to sum\n", value);
+
+		sum += value;
+	}*/
+
+	// A more reliable way of repeatedly reading from a file is checking
+	// the return value of fscanf. On success, fscanf will return the number
+	// of values read.
+	while (fscanf(infile, "%lf", &value) == 1) {
+		printf("(fscanf) Adding value %.2lf to sum\n", value);
+
+		sum += value;
+	}
+
+	fclose(infile);
+
+	return sum;
+}
+