lang/AST.txt at master · rahulraocoder/lang · GitHub

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define statement as:
S01	REM text                     <-----ignored
S02	;
S03	return;
S04	return expression;           <-----evaluates to r = expression; return;
S05	expression;
S06	def <var>;
S07	undef <var>;
S08	<var> = expression;
S09	proc <func> = [ statements ];
S10	procdef <func>;
S11	delete <var>;
S12	print expression;
S13	printc expression;
S14	read <var>;
S15	readc <var>;
S16	call <func>;
S17	push expression;
S18	pop <var>;
S19	parse('filename');
S20	if (expression) -> <func> : <func>;
S21	/* text */

define expression as:
E01	term
E02	term + expression
E03	term - expression

define term as:
T01	factor
T02	factor * expression
T03	factor / expression
T04	(expression)

define factor as:
F01	constant
F02	variable

sample: (see /lang/examples)

S->REM Txt()
S->;
S->return;
S->return E();
S->E();
S->def V();
S->undef V();
S->V() = E();
S->proc V() = [ Ss() ];
S->procdef V();
S->delete V();
S->print E();
S->printc E();
S->read V();
S->readc V();
S->call V();
S->push E();
S->pop V();
S->parse('Fname()');
S->if (E()) -> V() : V();

E->T()
E->T() + E()
E->T() - E()

T->F()
T->F() * E()
T->F() / E()
T->(E())

F->CONSTANT
F->VARIABLE