From f9f62e75f3b234b5daf3bc25e995f9f0f56ca0a2 Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Fri, 11 Jun 2021 10:34:27 +0530
Subject: add prog 15

---
 15/main.l | 23 ++++++++++++++++++++
 15/main.y | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 15/main.l
 create mode 100644 15/main.y

(limited to '15')

diff --git a/15/main.l b/15/main.l
new file mode 100644
index 0000000..ffcb97e
--- /dev/null
+++ b/15/main.l
@@ -0,0 +1,23 @@
+%{
+#include <stdlib.h>
+extern int yylval;
+%}
+
+%%
+
+[0-9]+? {
+    yylval=yytext[0];
+    return NUM;
+};
+[a-zA-Z]+? {
+    yylval=yytext[0];
+    return IDENT;
+}
+. return yytext[0];
+\n return 0;
+%%
+
+int yywrap() {
+    return 1;
+}
+
diff --git a/15/main.y b/15/main.y
new file mode 100644
index 0000000..46075c2
--- /dev/null
+++ b/15/main.y
@@ -0,0 +1,73 @@
+%{
+#include<stdio.h>
+#include<string.h>
+#include<stdlib.h>
+#include<ctype.h>
+
+void apply(char);
+void load_num(char);
+void load_var(char);
+void store_var(char);
+
+int yyerror(char *);
+int yylex();
+int reg_count=0;
+struct instruction {
+    char op1;
+    char op2;
+    char opr;
+};
+%}
+
+%token IDENT NUM
+%type expr
+%left '+'
+%left '*''/'
+%left '-'
+%%
+
+statement: IDENT '=' expr ';' { store_var((char)$1); }
+         ;
+
+expr: expr '+' expr {apply('+');}
+    | expr '-' expr {apply('-');}
+    | expr '*' expr {apply('*');}
+    | NUM {load_num((char)$1); $$=(char)$1;}
+    | IDENT {load_var((char)$1); $$=(char)$1;}
+    ;
+
+%%
+
+void apply(char opr) {
+    switch(opr) {
+        case '+': 
+            printf("ADD ");
+            break;
+        case '-': 
+            printf("SUB ");
+            break;
+        case '*': printf("MUL ");
+    }
+    printf("R%d, R%d, R%d\n", reg_count-2, reg_count-2, reg_count-1);
+}
+
+void load_num(char num) {
+    printf("LD R%d, #%c\n", reg_count++, num);
+}
+
+void load_var(char var) {
+    printf("LD R%d, %c\n", reg_count++, var);
+}
+
+void store_var(char var) {
+    printf("ST %c, R%d\n", var, reg_count-1);
+}
+
+int yyerror(char *s) {
+    printf("ERROR: %s",s);
+    exit(0);
+}
+
+int main() {
+    yyparse();
+}
-- 
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