From ce9248385c8d02141fb9eee7ea14894d4f323686 Mon Sep 17 00:00:00 2001
From: bnewbold <bnewbold@robocracy.org>
Date: Fri, 4 Mar 2011 18:40:07 -0500
Subject: backup of stuffs

---
 libraries         |  11 +++++
 notes             |  10 +++++
 rpn.c             | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 test_ascii_enum.c |  21 +++++++++
 4 files changed, 171 insertions(+)
 create mode 100644 libraries
 create mode 100644 notes
 create mode 100644 rpn.c
 create mode 100644 test_ascii_enum.c

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");
+}
+
-- 
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