lib/expr: add left/right shifting operators

apps/README.md

@@ -91,8 +91,12 @@ this way, it's going to mess with the parser.
 
 An expression is a bunch of literals or symbols assembled by operators.
 Supported operators are `+`, `-`, `*`, `/`, `%` (modulo), `&` (bitwise and),
-`|` (bitwise or) and `^` (bitwise xor). Bitwise operator always operate on
-the whole 16-bits.
+`|` (bitwise or), `^` (bitwise xor), `{` (shift left), `}` (shift right).
+Bitwise operator always operate on the whole 16-bits.
+
+Shift operators break from the `<<` and `>>` tradition because the complexity
+if two-sized operator is significant and deemed not worth it. The shift
+operator shift the left operand X times, X being the right operand.
 
 There is no parenthesis support yet.
 

apps/lib/expr.asm

@@ -123,6 +123,10 @@ exprTbl:
 	.dw	.or
 	.db	'^'
 	.dw	.xor
+	.db	'}'
+	.dw	.rshift
+	.db	'{'
+	.dw	.lshift
 	.db	0		; end of table
 
 .plus:
@@ -198,3 +202,35 @@ exprTbl:
 	push	hl \ pop ix
 	cp	a		; ensure Z
 	ret
+
+.rshift:
+	push	ix \ pop hl
+	ld	a, l
+	and	0xf
+	ret	z
+	push	bc
+	ld	b, a
+.rshiftLoop:
+	srl	d
+	rr	e
+	djnz	.rshiftLoop
+	push	de \ pop ix
+	pop	bc
+	cp	a		; ensure Z
+	ret
+
+.lshift:
+	push	ix \ pop hl
+	ld	a, l
+	and	0xf
+	ret	z
+	push	bc
+	ld	b, a
+.lshiftLoop:
+	sla	e
+	rl	d
+	djnz	.lshiftLoop
+	push	de \ pop ix
+	pop	bc
+	cp	a		; ensure Z
+	ret

tools/tests/unit/test_expr.asm

@@ -145,6 +145,10 @@ testParseExpr:
 	call	.testEQ
 	ld	iy, .t5
 	call	.testEQ
+	ld	iy, .t6
+	call	.testEQ
+	ld	iy, .t7
+	call	.testEQ
 	ret
 
 .testEQ:
@@ -176,6 +180,12 @@ testParseExpr:
 .t5:
 	.dw	0x96f8
 	.db	"0x99f7^0x0f0f", 0
+.t6:
+	.dw	0x133e
+	.db	"0x99f7}3", 0
+.t7:
+	.dw	0xcfb8
+	.db	"0x99f7{3", 0
 
 nexttest:
 	ld	a, (testNum)