handle truncation in entering numbers properly

src/decn/decn.c

@@ -316,7 +316,6 @@ void build_dec80(__xdata const char* signif_str, __xdata exp_t exponent){
 				// adjust exponent for left-aligned significand input
 				// or for number of digits past decimal point
 				if (num_lr_points > 0){ //left count exists
-					assert(DEC80_NUM_LSU*2 > num_lr_points);
 					new_exponent = exponent + (num_lr_points - 1); //1 digit left of implicit point
 					//overflow is checked later, should be impossible to overflow int16_t:
 					assert(new_exponent >= exponent);

src/decn/decn_tests.cpp

@@ -110,6 +110,10 @@ TEST_CASE("build decn"){
 	decn_to_str_complete(&AccDecn);
 	CHECK_THAT(Buf, Equals("123456789012345678."));
 
+	build_dec80("12345678901234567890", +2);
+	decn_to_str_complete(&AccDecn);
+	CHECK_THAT(Buf, Equals("1.23456789012345678E21"));
+
 	//overflow
 	build_dec80("100", DEC80_MAX_EXP-1);
 	decn_to_str_complete(&AccDecn);