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-rw-r--r--ex4-2.c130
-rw-r--r--ex4-3.c113
2 files changed, 243 insertions, 0 deletions
diff --git a/ex4-2.c b/ex4-2.c
new file mode 100644
index 0000000..8a57575
--- /dev/null
+++ b/ex4-2.c
@@ -0,0 +1,130 @@
+#include <stdio.h>
+
+/*static int _strlen(char s[]) {
+ int i;
+ for (i=0; s[i] != '\0'; i++) {}
+ return i;
+}*/
+
+/*static int _isspace(char s) {
+ return s == ' ' || s == '\t';
+}*/
+
+static int _isdigit(char s) {
+ return '0' <= s && s <= '9';
+}
+
+static int _abs(int a) {
+ if (a >=0) {
+ return a;
+ } else {
+ return -1 * a;
+ }
+}
+
+static int _intval(char s) {
+ return s - '0';
+}
+
+static int _isupper(char s) {
+ return 'A' <= s && s <= 'Z';
+}
+
+static char _tolower(char s) {
+ static int diff = 'A' - 'a';
+ if (_isupper(s)) {
+ return s - diff;
+ } else {
+ return s;
+ }
+}
+
+
+static int _atoi_internal(char s[], int n) {
+ if (s == NULL || *s == '\0' || !_isdigit(*s)) {
+ return n;
+ }
+ __attribute__((musttail)) // Functional programinng enabler :)
+ return _atoi_internal(s + 1, (10 * n) + _intval(*s));
+}
+/**
+ * Converts a string to an integer
+ * string must be null terminated
+ * overflow isn't detected, int is the limit
+ */
+int _atoi(char s[]) {
+ int i = 0;
+ int sign = (s[i] == '-') ? -1 : 1;
+ if (s[i] == '+' || s[i] == '-')
+ i++;
+ return _atoi_internal(s + i, 0) * sign;
+}
+
+/**
+ * Converts a string to a double
+ *
+ * string must be null terminated.
+ * overflow isn't detected, and double precision is the limit.
+ */
+double _atof(char s[]) {
+ double val, power, ee;
+ int i = 0;
+ int sign = (s[i] == '-') ? -1 : 1;
+ if (s[i] == '+' || s[i] == '-')
+ i++;
+ for (val = 0.0; _isdigit(s[i]); i++)
+ val = 10.0 * val + _intval(s[i]);
+ if (s[i] == '.')
+ i++;
+ for (power = 1.0; _isdigit(s[i]); i++) {
+ val = 10.0 * val + _intval(s[i]);
+ power *= 10.0;
+ }
+ ee = 1.0;
+ if (_tolower(s[i]) == 'e') {
+ i++;
+ int exponent = _atoi(s + i);
+ if (exponent >= 0) {
+ for (int j=0;j<_abs(exponent);j++) ee *= 10.0;
+ } else {
+ for (int j=0;j<_abs(exponent);j++) ee /= 10.0;
+ }
+ }
+ return (sign * val / power) * ee;
+
+}
+
+void testb(char s[]) {
+ printf("atoi s = [%s] result = [%d]\n", s, _atoi(s));
+}
+
+void test(char s[]) {
+ printf("atof s = [%s] result = [%lf]\n", s, _atof(s));
+}
+
+int main(void) {
+ test("");
+ test("gibber");
+ test("\0");
+ test("1");
+ test("1.0");
+ test("99.0");
+ test("-10.0");
+ test("+11.0");
+ test("++11.0");
+ test("-11111111111111111111111111111111111111111111111111111111111111111111111111111111111.1");
+
+ testb("gibber");
+ testb("");
+ testb("\0");
+ testb("1");
+ testb("1.5");
+ testb("+2.6");
+ testb("-7.8");
+ testb("--7.8");
+
+ test("+11.0e5");
+ test("2.75345e3");
+ test("2.75345e-3");
+ test("2.75345E-3");
+} \ No newline at end of file
diff --git a/ex4-3.c b/ex4-3.c
new file mode 100644
index 0000000..47689f4
--- /dev/null
+++ b/ex4-3.c
@@ -0,0 +1,113 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+#define NUMBER '0'
+#define MAXOP 100
+#define MAXVAL 100
+
+int getop(char[]);
+void push(double);
+double pop(void);
+
+/**
+ * Reverse polish notation calculator
+ */
+int main(void) {
+ int type;
+ double op2;
+ char s[MAXOP];
+ while ((type = getop(s)) != EOF) {
+ switch (type) {
+ case NUMBER:
+ push(atof(s));
+ break;
+ case '+':
+ push(pop() + pop());
+ break;
+ case '*':
+ push(pop() * pop());
+ break;
+ case '-':
+ op2 = pop();
+ push(pop() - op2);
+ break;
+ case '/':
+ op2 = pop();
+ if (op2 != 0.0)
+ push(pop() / op2);
+ else
+ printf("error: zero division attempted!\n");
+ break;
+ case '\n':
+ printf("\t%.8g\n", pop());
+ break;
+ default:
+ printf("unknown command %s\n", s);
+ break;
+ }
+ }
+ return 0;
+}
+
+
+int sp; // Stack position
+double val[MAXVAL]; // Value stack
+void push(double f) {
+ if (sp < MAXVAL) {
+ val[sp++] = f;
+ } else {
+ printf("error, stack full\n");
+ }
+}
+
+double pop(void) {
+ if (sp >= 0) {
+ return val[--sp];
+ } else {
+ printf("error, empty stack\n");
+ return 0.0;
+ }
+}
+
+
+int getch(void);
+void ungetch(int);
+
+int getop(char s[]) {
+ int i,c;
+ // Skip to teh first non-space or tab character
+ while ((s[0] = c = getch()) == ' ' || c == '\t');
+ // Then add a null for some reason?
+ s[1] = '\0';
+ // if it's not a part of a number, it's an operation
+ if (!isdigit(c) && c != '.')
+ return c;
+ // Integer part
+ i = 0;
+ if (isdigit(c))
+ while (isdigit(s[++i] = c = getch()));
+ // fraction part
+ if (c == '.')
+ while (isdigit(s[++i] = c = getch()));
+ s[i] = '\0';
+ if (c != EOF)
+ ungetch(c);
+ return NUMBER;
+}
+
+#define BUFSIZE 100
+
+char buf[BUFSIZE]; // buffer for ungetch
+int bufp = 0; // next free in buf
+
+int getch(void) {
+ return (bufp > 0) ? buf[--bufp] : getchar();
+}
+
+void ungetch(int c) {
+ if (bufp >= BUFSIZE)
+ printf("ungetch: buffer full\n");
+ else
+ buf[bufp++] = c;
+} \ No newline at end of file