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-rw-r--r--libraries11
-rw-r--r--notes10
-rw-r--r--rpn.c129
-rw-r--r--test_ascii_enum.c21
4 files changed, 171 insertions, 0 deletions
diff --git a/libraries b/libraries
new file mode 100644
index 0000000..e570fe0
--- /dev/null
+++ b/libraries
@@ -0,0 +1,11 @@
+
+diet libc
+http://www.fefe.de/dietlibc/
+
+libowfat (is libdjb...)
+http://www.fefe.de/libowfat/
+
+"standard function library"
+
+glibc
+
diff --git a/notes b/notes
new file mode 100644
index 0000000..8c4954c
--- /dev/null
+++ b/notes
@@ -0,0 +1,10 @@
+
+Can use 'const' in function parameters to indicate to the compiler that a
+variable will not be modified.
+
+The order of evaluation (function calls) in an expression is undefined. Eg:
+
+ push(pop() + pop()) is ok
+ push(pop() - pop()) is NOT ok
+
+
diff --git a/rpn.c b/rpn.c
new file mode 100644
index 0000000..d1c72ad
--- /dev/null
+++ b/rpn.c
@@ -0,0 +1,129 @@
+/* rpn.c
+ *
+ * Takes a string of reverse polish notation math and pretty-prints it with
+ * parenthesis. Recognizes the {*, +, -, /} operators and ignores everything
+ * else.
+ *
+ */
+
+/*
+- tree data structure
+- read in integer function (std?)
+
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#define LINE_LEN 1024
+
+struct rpn_node {
+ char val;
+ struct rpn_node *left;
+ struct rpn_node *right;
+};
+
+int rpn_parse(char s[], struct rpn_node *node);
+void rpn_print(struct rpn_node *node);
+int rpn_eval(struct rpn_node *node);
+int isoper(char c);
+
+int main(void) {
+ char line[LINE_LEN] = "";
+ struct rpn_node root_node;
+ char tc;
+ int i,j;
+
+ // read string
+ fgets(line, LINE_LEN, stdin);
+
+ // reverse it
+ j = strlen(line) - 1;
+ for(i = 0; i <= j/2; i++) {
+ tc = line[i];
+ line[i] = line[j-i];
+ line[j-i] = tc;
+ }
+
+ // parse it down to single char numbers and opers
+ for(i = j = 0; i < strlen(line); i++) {
+ if(isdigit(line[i]) || isoper(line[i]))
+ line[j++] = line[i];
+ }
+ line[j] = '\0';
+ //printf("Compressed: %s\n", line);
+
+ // recursively parse down and store result in right; then recursively parse
+ // down and store result in left
+ rpn_parse(line, &root_node);
+
+ // spider down the tree to the left, printing
+ rpn_print(&root_node);
+ printf(" = %d\n", rpn_eval(&root_node));
+ return;
+ // &new_node = malloc(sizeof(struct node))
+}
+
+// returns the number of characters that got chomped up
+int rpn_parse(char s[], struct rpn_node *node) {
+ int i=0;
+
+ node->val = s[0];
+ i++;
+ //printf("Got len=%d, isoper=%d: %s\n", (int)strlen(s), isoper(s[0]), s);
+
+ if(isoper(s[0])) {
+ //printf("Got an oper: %c\n", s[0]);
+ // load up right and left
+ node->right = malloc(sizeof(struct rpn_node));
+ node->left = malloc(sizeof(struct rpn_node));
+ i += rpn_parse(&s[i], node->right);
+ i += rpn_parse(&s[i], node->left);
+ }
+ return i;
+}
+
+void rpn_print(struct rpn_node *node) {
+ if(isoper(node->val)) {
+ printf("(");
+ rpn_print(node->left);
+ printf(" %c ", node->val);
+ rpn_print(node->right);
+ printf(")");
+ } else {
+ printf("%c", node->val);
+ }
+}
+
+int isoper(char c) {
+ switch(c) {
+ case '+':
+ case '-':
+ case '*':
+ case '/':
+ return 1;
+ break;
+ default:
+ return 0;
+ }
+}
+
+int rpn_eval(struct rpn_node *node) {
+ if(isdigit(node->val)) {
+ return node->val - '0';
+ }
+ switch(node->val) {
+ case '+':
+ return rpn_eval(node->left) + rpn_eval(node->right);
+ case '-':
+ return rpn_eval(node->left) - rpn_eval(node->right);
+ case '*':
+ return rpn_eval(node->left) * rpn_eval(node->right);
+ case '/':
+ return rpn_eval(node->left) / rpn_eval(node->right);
+ default:
+ printf("ERROR: unexpected character '%c'.", node->val);
+ exit(-1);
+ }
+}
diff --git a/test_ascii_enum.c b/test_ascii_enum.c
new file mode 100644
index 0000000..55a5724
--- /dev/null
+++ b/test_ascii_enum.c
@@ -0,0 +1,21 @@
+
+#include <stdio.h>
+#include <string.h>
+
+enum { FIRST, SECOND, THIRD };
+
+char list[] = "abcABC123(){}";
+
+void main(void) {
+ int i;
+ printf("EOF: 0x%X\n", EOF);
+ printf("FIRST: 0x%X\n", FIRST);
+ printf("SECOND: 0x%X\n", SECOND);
+ printf("THIRD: 0x%X\n", THIRD);
+ for(i = 0; i <= strlen(list); i++)
+ printf("list[%d]: %c = 0x%X\n", i, list[i], list[i]);
+
+ printf("Does list[%d] == FIRST? %s!\n", (int)strlen(list),
+ list[strlen(list)] == FIRST ? "YES" : "NO");
+}
+