From 8cca4d1fe83f792d0f3c5dd897611ea2ff441de0 Mon Sep 17 00:00:00 2001
From: rodri <rgl@antares-labs.eu>
Date: Sat, 31 Aug 2024 16:07:15 +0000
Subject: stage 3.

---
 s3/rhoc.y | 172 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 172 insertions(+)
 create mode 100644 s3/rhoc.y

(limited to 's3/rhoc.y')

diff --git a/s3/rhoc.y b/s3/rhoc.y
new file mode 100644
index 0000000..ea62b13
--- /dev/null
+++ b/s3/rhoc.y
@@ -0,0 +1,172 @@
+%{
+#include "dat.h"
+%}
+%union {
+	double val;
+	Symbol *sym;
+}
+%token	<val> NUMBER
+%token	<sym> VAR CONST BLTIN UNDEF
+%type	<val> expr asgn
+%right	'='
+%left	'+' '-'
+%left	'*' '/'
+%left	'%'
+%right	'^'
+%left	UMINUS
+%%
+list:	/* ε */
+	| list '\n'
+	| list asgn '\n'
+	| list expr '\n'	{ print("\t%.8g\n", $2); }
+	| list error '\n'	{ yyerrok; }
+	;
+asgn:	  VAR '=' expr
+	{
+		if($1->type == CONST)
+			rterror("assignment to constant");
+		$$ = $1->u.val = $3;
+		$1->type = VAR;
+	}
+	;
+expr:	  NUMBER
+	| VAR
+	{
+		if($1->type == UNDEF)
+			rterror("undefined variable");
+		$$ = $1->u.val;
+	}
+	| asgn
+	| BLTIN '(' expr ')'	{ $$ = $1->u.fn($3); }
+	| '-' expr	%prec UMINUS { $$ = -$2; }
+	| expr '+' expr		{ $$ = $1 + $3; }
+	| expr '-' expr 	{ $$ = $1 - $3; }
+	| expr '*' expr 	{ $$ = $1 * $3; }
+	| expr '/' expr
+	{
+		if($3 == 0)
+			rterror("division by zero");
+		$$ = $1 / $3;
+	}
+	| expr '%' expr 	{ $$ = fmod($1, $3); }
+	| expr '^' expr 	{ $$ = pow($1, $3); }
+	| expr '(' expr ')'	{ $$ = $1 * $3; }
+	| '(' expr ')'		{ $$ = $2; }
+	;
+%%
+#include <u.h>
+#include <libc.h>
+#include <ctype.h>
+#include <bio.h>
+#include "fns.h"
+
+Biobuf *bin;
+jmp_buf begin;
+int lineno;
+int prompt;
+
+void *
+emalloc(ulong n)
+{
+	void *p;
+
+	p = malloc(n);
+	if(p == nil)
+		sysfatal("malloc: %r");
+	memset(p, 0, n);
+	setmalloctag(p, getcallerpc(&n));
+	return p;
+}
+
+void
+yyerror(char *msg)
+{
+	fprint(2, "%s at line %d\n", msg, lineno);
+}
+
+void
+rterror(char *msg)
+{
+	fprint(2, "%s at line %d\n", msg, lineno-1);
+	longjmp(begin, 0);
+}
+
+int
+catch(void *ureg, char *msg)
+{
+	if(strncmp(msg, "sys: fp", 7) == 0){
+		yyerror("floating point exception");
+		notejmp(ureg, begin, 0);
+	}
+	return 0;
+}
+
+int
+yylex(void)
+{
+	Symbol *s;
+	char sname[256], *p;
+	Rune r;
+
+	if(prompt){
+		print("%d: ", lineno);
+		prompt--;
+	}
+	while((r = Bgetrune(bin)) == ' ' || r == '\t')
+		;
+	if(r == Beof)
+		return 0;
+	if(r == '.' || isdigitrune(r)){
+		Bungetrune(bin);
+		Bgetd(bin, &yylval.val);
+		return NUMBER;
+	}
+	if(isalpharune(r)){
+		p = sname;
+		do{
+			if(p+runelen(r) - sname >= sizeof(sname))
+				return r; /* force syntax error. */
+			p += runetochar(p, &r);
+		}while((r = Bgetrune(bin)) != Beof &&
+			(isalpharune(r) || isdigitrune(r)));
+		Bungetrune(bin);
+		*p = 0;
+		if((s = lookup(sname)) == nil)
+			s = install(sname, UNDEF, 0);
+		yylval.sym = s;
+		return s->type == UNDEF || s->type == CONST ? VAR : s->type;
+	}
+	if(r == '\n'){
+		lineno++;
+		prompt++;
+	}
+	return r;
+}
+
+void
+usage(void)
+{
+	fprint(2, "usage: %s\n", argv0);
+	exits("usage");
+}
+
+void
+main(int argc, char *argv[])
+{
+	ARGBEGIN{
+	default: usage();
+	}ARGEND;
+	if(argc > 0)
+		usage();
+	atnotify(catch, 1);
+	bin = Bfdopen(0, OREAD);
+	if(bin == nil)
+		sysfatal("Bfdopen: %r");
+	lineno++;
+	prompt++;
+	init();
+	setjmp(begin);
+	yyparse();
+	Bterm(bin);
+	exits(0);
+}
-- 
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