Implement === and !== string comparison operators (#1832)

man/rgbasm.5

@@ -586,6 +586,19 @@ is equivalent to
 or to
 .Ql STRCAT("str", \&"ing") .
 .Pp
+You can use the 
+.Sq ===
+and
+.Sq !==
+operators to compare two strings.
+.Ql \&"str" === \&"ing"
+is equivalent to
+.Ql STRCMP("str", \&"ing") == 0 ,
+and
+.Ql \&"str" !== \&"ing"
+is equivalent to
+.Ql STRCMP("str", \&"ing") != 0 .
+.Pp
 The following functions operate on string expressions, and return strings themselves.
 .Bl -column "STRSLICE(str, start, stop)"
 .It Sy Name Ta Sy Operation

src/asm/lexer.cpp

@@ -1750,14 +1750,22 @@ static Token yylex_NORMAL() {
 		case '^': // Either ^= or XOR
 			return oneOrTwo('=', T_(POP_XOREQ), T_(OP_XOR));
 
-		case '=': // Either assignment or EQ
-			return oneOrTwo('=', T_(OP_LOGICEQU), T_(POP_EQUAL));
-
-		case '!': // Either a NEQ or negation
-			return oneOrTwo('=', T_(OP_LOGICNE), T_(OP_LOGICNOT));
-
 			// Handle ambiguous 1-, 2-, or 3-char tokens
 
+		case '=': // Either assignment, EQ or string EQ
+			if (peek() == '=') {
+				shiftChar();
+				return oneOrTwo('=', T_(OP_STREQU), T_(OP_LOGICEQU));
+			}
+			return Token(T_(POP_EQUAL));
+
+		case '!': // Either negation, NEQ, or string NEQ
+			if (peek() == '=') {
+				shiftChar();
+				return oneOrTwo('=', T_(OP_STRNE), T_(OP_LOGICNE));
+			}
+			return Token(T_(OP_LOGICNOT));
+
 		case '<': // Either <<=, LT, LTE, or left shift
 			if (peek() == '<') {
 				shiftChar();

src/asm/parser.y

@@ -107,6 +107,7 @@
 
 // String operators
 %token OP_CAT "++"
+%token OP_STREQU "===" OP_STRNE "!=="
 
 // Comparison operators
 %token OP_LOGICEQU "==" OP_LOGICNE "!="
@@ -1287,6 +1288,12 @@ relocexpr_no_str:
 	| CHARACTER {
 		$$.makeNumber(act_CharToNum($1));
 	}
+	| string OP_STREQU string {
+		$$.makeNumber($1.compare($3) == 0);
+	}
+	| string OP_STRNE string {
+		$$.makeNumber($1.compare($3) != 0);
+	}
 	| OP_LOGICNOT relocexpr %prec NEG {
 		$$.makeUnaryOp(RPN_LOGNOT, std::move($2));
 	}

test/asm/string-compare.asm

@@ -0,0 +1,7 @@
+assert "hello" === "hello"
+assert "hello" !== "goodbye"
+assert "game" ++ "boy" === "gameboy"
+assert "fire flower" === "fire" ++ " " ++ "flower"
+assert "a" === "b" == 0
+assert 1 == "a" !== "b"
+assert 1 + 2 * 3 ** "x" !== "y" == 7