# HG changeset patch
# User Masataka Kohagura <kohagura@cr.ie.u-ryukyu.ac.jp>
# Date 1433774409 -32400
# Node ID 883e3473a9f5f15114b9c33e0d43a06441be16ce
# Parent  f540de861cd64ebd2a3e7cb0c834d54ad9837130
fix

diff -r f540de861cd6 -r 883e3473a9f5 c/regexParser/main.cc
--- a/c/regexParser/main.cc	Mon Jun 08 15:47:52 2015 +0900
+++ b/c/regexParser/main.cc	Mon Jun 08 23:40:09 2015 +0900
@@ -1,29 +1,186 @@
+/*
+    Very Simple Calculator
+    $Id$
+ */
+
 #include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
 
-typedef struct node {
-    struct node *left;
-    struct node *right;
-    int type;
-    int value;
-} Node, *NodePtr;
+static char *ptr,*last_ptr;
+static int  value,lvalue;
+static int  last_token;
+static int  variable[48];
+
+static int  expr();
+static int  aexpr();
+static int  mexpr();
+static int  term();
+static int  token();
+static void  error(char *);
 
 
-NodePtr newNode(int type, int value, NodePtr left, NodePtr right) {
-    NodePtr d = (NodePtr)malloc(sizeof(Node));
-    d->type = type;
-    d->value = value;
-    d->left = left;
-    d->right = right;
-    return d;
+static int
+token()
+{
+    int c,d;
+
+    last_ptr = ptr;  /* for error position */
+    c= *ptr;
+    if(!c) {
+        last_token = EOF;
+        return last_token;
+    }
+    ptr++;
+    if (c<=' ') {       /* comment */
+        while(*ptr++);
+            ptr--;
+            last_token = EOF;
+            last_ptr = ptr;
+            return last_token;
+    }
+
+    if('0'<=c && c<='9') {     /* Decimal */
+        d = c-'0';
+        while((c= *ptr++)) {
+            if('0'<=c && c<='9') {
+                d = d*10 + (c - '0');
+            } else {
+                break;
+            }
+        }
+        c && ptr--;
+        value = d;
+        last_token = '0';
+        return last_token;
+
+    } else if ('a'<=c && c<='z') {    /* variable */
+        value = c-'a';                /* return variable reference */
+        last_token = 'v';
+        return last_token;
+    } else {
+        last_token = c;
+        return last_token;
+        return c;
+    }
+}
+
+static int
+expr()
+{
+    int d,assign;
+
+    d = aexpr();
+    assign = lvalue;
+    switch(last_token) {
+    case '>':
+        d = (d > aexpr());
+        return d;
+    case '=':
+        if(assign>=0) {
+            d = expr(); 
+            variable[assign] = d;
+            return d;
+        } else {
+            error("Bad assignment");
+            return 0;
+        }
+    case ')':
+        return d;
+    case EOF:
+        return d;
+    default:
+        error("Bad expression");
+        return d;
+    }
 }
 
-int main(int argc, char **argv) {
+static int
+aexpr()
+{
+    int d;
+
+    d = mexpr();
+    switch(last_token) {
+    case '-':
+        d -= aexpr();
+        return d;
+    case '+':
+        d += aexpr();
+        return d;
+    default:
+        return d;
+    }
+}
+
+static int
+mexpr()
+{
+    int d;
+    d = term();
+    switch(last_token) {
+    case '*':
+        d *= mexpr();
+        return d;
+    case '/':
+        d /= mexpr();
+        return d;
+    default:
+        return d;
+    }
+}
+
+static int
+term()
+{
+    int d;
 
-    for (int i = 1; i < argc ; i++) {
+    lvalue= -1;
+    token();
+    if(last_token==EOF) {
+        error("Term expected");
+    }
+    switch(last_token) {
+    case '0':
+        d = value;
+        token();
+        return d;
+    case 'v':
+        d = lvalue = value;
+        token();
+        return variable[d];
+    case '(':
+        d = expr();
+        if(last_token != ')') {
+            error("Unbalanced parenthsis");
+        }
+        token();
+        return d;
+    default:
+        token();
+        error("Unknown term");
+        return 0;
+    }
+}
 
+static int lineno = 0;
+
+void
+error(char *msg)
+{
+    fprintf(stderr,"%s on line %d\n",msg, lineno);
+}
+
+int
+main()
+{
+    int d;
+    char buf[BUFSIZ];
+
+    while (fgets(buf,BUFSIZ,stdin)) {
+        ptr = buf;
+        d = expr();
+        printf("%s = 0x%08x = %d\n",buf,d,d);
+        fflush(stdout);
+        lineno++;
     }
-
     return 0;
 }