Add "let name = value, ... ;" to create local variables.

minproto.leg

@@ -1,6 +1,6 @@
 # minproto.leg -- minimal prototype langauge for semantic experiments
 #
-# last edited: 2024-05-09 10:17:11 by piumarta on zora-1034.local
+# last edited: 2024-05-09 11:30:35 by piumarta on zora-1034.local
 
 %{
 ;
@@ -85,9 +85,9 @@ typedef oop (*prim_t)(oop func, oop self, oop args, oop env);
 #endif
 
 #if PRIMCLOSURE
-#define doProtos(_) _(Object) _(GetVar) _(SetVar) _(GetProp) _(SetProp) _(GetArray) _(SetArray) _(Call) _(Invoke) _(Binop) _(Unyop) _(If) _(While) _(Block) _(For) _(ForIn) _(ForFromTo) _(Literal)
+#define doProtos(_) _(Object) _(GetVar) _(SetVar) _(GetProp) _(SetProp) _(GetArray) _(SetArray) _(Call) _(Invoke) _(Binop) _(Unyop) _(Let) _(If) _(While) _(Block) _(For) _(ForIn) _(ForFromTo) _(Literal)
 #else
-#define doProtos(_) _(Object) _(GetVar) _(SetVar) _(GetProp) _(SetProp) _(GetArray) _(SetArray) _(Call) _(Invoke) _(Binop) _(Unyop) _(If) _(While) _(Block) _(For) _(ForIn) _(ForFromTo) _(Literal) _(Lambda) _(Closure)
+#define doProtos(_) _(Object) _(GetVar) _(SetVar) _(GetProp) _(SetProp) _(GetArray) _(SetArray) _(Call) _(Invoke) _(Binop) _(Unyop) _(Let) _(If) _(While) _(Block) _(For) _(ForIn) _(ForFromTo) _(Literal) _(Lambda) _(Closure)
 #endif
 
 #define  declareProto(NAME)	oop p##NAME = 0;
@@ -114,7 +114,7 @@ doTypes(makeProto);
 doProperties(declareProp);
 #undef declareProp
 
-#define doSymbols(_) _(t) _(name) _(expr) _(function) _(arguments) _(object) _(index) _(key) _(value) _(self) _(method) _(parameters) _(body) _(lambda) _(environment) _(operation) _(full) _(condition) _(consequent) _(alternate) _(expression) _(identifier) _(initialise) _(update) _(first) _(last) _(fixed)
+#define doSymbols(_) _(t) _(name) _(expr) _(function) _(arguments) _(object) _(index) _(key) _(value) _(self) _(method) _(parameters) _(body) _(lambda) _(environment) _(operation) _(full) _(condition) _(consequent) _(alternate) _(expression) _(identifier) _(initialise) _(update) _(first) _(last) _(fixed) _(keyvals)
 
 #define declareSym(NAME)	oop sym_##NAME = 0;
 doSymbols(declareSym);
@@ -1564,6 +1564,46 @@ void Unyop_codeOn(oop exp, oop str, oop env)
     codeOn(str, value, 0);
 }
 
+oop newLet(void)
+{
+    oop o = new(pLet);
+    Object_put(o, sym_keyvals, new(pObject));
+    return o;
+}
+
+oop Let_append(oop let, oop key, oop value)
+{
+    oop keyvals = Object_getLocal(let, sym_keyvals);
+    Object_push(keyvals, key);
+    Object_push(keyvals, value);
+    return let;
+}
+
+oop Let_eval(oop exp, oop env)
+{
+    oop  keyvals = Object_getLocal(exp, sym_keyvals);
+    oop *indexed =  get(keyvals, Object,indexed);
+    int  isize   = _get(keyvals, Object,isize);
+    oop  result  = nil;
+    for (int i = 0;  i < isize - 1;  i += 2)
+	Object_put(env, indexed[i], (result = eval(indexed[i+1], env)));
+    return result;
+}
+
+void Let_codeOn(oop exp, oop str, oop env)
+{
+    oop  keyvals = Object_getLocal(exp, sym_keyvals);
+    oop *indexed =  get(keyvals, Object,indexed);
+    int  isize   = _get(keyvals, Object,isize);
+    String_appendAll(str, "let ");
+    for (int i = 0;  i < isize - 1;  i += 2) {
+	if (i) String_appendAll(str, ", ");
+	codeOn(str, indexed[i], 0);
+	String_appendAll(str, " = ");
+	codeOn(str, indexed[i+1], 0);
+    }
+}
+
 oop newIf(oop condition, oop consequent, oop alternate)
 {
     oop o = new(pIf);
@@ -1871,7 +1911,10 @@ start	= - ( s:stmt				{ yysval = s }
 	    | < (!EOL .)* >			{ fatal("syntax error near: %s", yytext) }
 	    )
 
-stmt	= WHILE LPAREN c:expr RPAREN s:stmt	{ $$ = newWhile(c, s) }
+stmt	= LET l:mklet k:id ASSIGN v:expr	{ Let_append(l, k, v) }
+      	      ( COMMA k:id ASSIGN v:expr	{ Let_append(l, k, v) }
+	      )* SEMI				{ $$ = l }
+	| WHILE LPAREN c:expr RPAREN s:stmt	{ $$ = newWhile(c, s) }
 	| IF LPAREN c:expr RPAREN s:stmt
 	  ( ELSE t:stmt				{ $$ = newIf(c, s, t  ) }
 	  |					{ $$ = newIf(c, s, nil) }
@@ -1887,6 +1930,8 @@ stmt	= WHILE LPAREN c:expr RPAREN s:stmt	{ $$ = newWhile(c, s) }
 	| b:block				{ $$ = newBlock(b) }
 	| e:expr EOS				{ $$ = e }
 
+mklet	=					{ $$ = newLet() }
+
 proto	= v:var ( DOT j:id !LPAREN		{ v = newGetProp(v, j) }
 	  	)*    	   			{ $$ = v }
 
@@ -2028,6 +2073,7 @@ FOR	= "for"     !ALNUM  -
 IN	= "in"      !ALNUM  -
 FROM	= "from"    !ALNUM  -
 TO	= "to"      !ALNUM  -
+LET	= "let"     !ALNUM  -
 
 BQUOTE	= "`"      	-
 COMMAT	= "@"      	-