From 51f3bfd0e73d5e78d9fe71e6106a2a883619e18f Mon Sep 17 00:00:00 2001
From: rodri <rgl@antares-labs.eu>
Date: Sat, 31 Aug 2024 16:06:55 +0000
Subject: stage 1.

---
 s1/rhoc.y | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 s1/rhoc.y

(limited to 's1/rhoc.y')

diff --git a/s1/rhoc.y b/s1/rhoc.y
new file mode 100644
index 0000000..4015fc2
--- /dev/null
+++ b/s1/rhoc.y
@@ -0,0 +1,88 @@
+%{
+#define	YYSTYPE double
+%}
+%token	NUMBER
+%left	'+' '-'
+%left	'*' '/'
+%left	UNMIN
+%%
+list:	/* ε */
+	| list '\n'
+	| list expr '\n'	{ print("\t%.8g\n", $2); }
+	;
+expr:	  NUMBER
+	| '-' expr	%prec UNMIN { $$ = -$2; }
+	| expr '+' expr		{ $$ = $1 + $3; }
+	| expr '-' expr 	{ $$ = $1 - $3; }
+	| expr '*' expr 	{ $$ = $1 * $3; }
+	| expr '/' expr 	{ $$ = $1 / $3; }
+	| expr '%' expr 	{ $$ = fmod($1, $3); }
+	| expr '(' expr ')'	{ $$ = $1 * $3; }
+	| '(' expr ')'		{ $$ = $2; }
+	;
+%%
+#include <u.h>
+#include <libc.h>
+#include <ctype.h>
+#include <bio.h>
+
+Biobuf *bin;
+int lineno;
+int prompt;
+
+int yyparse(void);
+
+void
+yyerror(char *msg)
+{
+	fprint(2, "%s at line %d\n", msg, lineno);
+}
+
+int
+yylex(void)
+{
+	int c;
+
+	if(prompt){
+		print("%d: ", lineno);
+		prompt--;
+	}
+	while((c = Bgetc(bin)) == ' ' || c == '\t')
+		;
+	if(c == '.' || isdigit(c)){
+		Bungetc(bin);
+		Bgetd(bin, &yylval);
+		return NUMBER;
+	}
+	if(c == '\n'){
+		lineno++;
+		prompt++;
+	}
+	return c;
+}
+
+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();
+	bin = Bfdopen(0, OREAD);
+	if(bin == nil)
+		sysfatal("Bfdopen: %r");
+	lineno++;
+	prompt++;
+	yyparse();
+	Bterm(bin);
+	exits(0);
+}
-- 
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