Plan 9's rc.

not a clear win over byron's,
but at least it has the right syntax.

src/cmd/rc/var.c

@@ -0,0 +1,71 @@
+#include "rc.h"
+#include "exec.h"
+#include "fns.h"
+int hash(char *s, int n)
+{
+	register int h=0, i=1;
+	while(*s) h+=*s++*i++;
+	h%=n;
+	return h<0?h+n:h;
+}
+#define	NKW	30
+struct kw{
+	char *name;
+	int type;
+	struct kw *next;
+}*kw[NKW];
+void kenter(int type, char *name)
+{
+	register int h=hash(name, NKW);
+	register struct kw *p=new(struct kw);
+	p->type=type;
+	p->name=name;
+	p->next=kw[h];
+	kw[h]=p;
+}
+void kinit(void){
+	kenter(FOR, "for");
+	kenter(IN, "in");
+	kenter(WHILE, "while");
+	kenter(IF, "if");
+	kenter(NOT, "not");
+	kenter(TWIDDLE, "~");
+	kenter(BANG, "!");
+	kenter(SUBSHELL, "@");
+	kenter(SWITCH, "switch");
+	kenter(FN, "fn");
+}
+tree *klook(char *name)
+{
+	struct kw *p;
+	tree *t=token(name, WORD);
+	for(p=kw[hash(name, NKW)];p;p=p->next)
+		if(strcmp(p->name, name)==0){
+			t->type=p->type;
+			t->iskw=1;
+			break;
+		}
+	return t;
+}
+var *gvlook(char *name)
+{
+	int h=hash(name, NVAR);
+	var *v;
+	for(v=gvar[h];v;v=v->next) if(strcmp(v->name, name)==0) return v;
+	return gvar[h]=newvar(strdup(name), gvar[h]);
+}
+var *vlook(char *name)
+{
+	var *v;
+	if(runq)
+		for(v=runq->local;v;v=v->next)
+			if(strcmp(v->name, name)==0) return v;
+	return gvlook(name);
+}
+void setvar(char *name, word *val)
+{
+	register struct var *v=vlook(name);
+	freewords(v->val);
+	v->val=val;
+	v->changed=1;
+}