Add polynomial addition and substraction in ring.

2 files changed, 38 insertions, 11 deletions

diff --git a/README.md b/README.md
index e25daa9..e109b02 100644
--- a/README.md
+++ b/README.md
@@ -18,18 +18,22 @@ $ make run_poly_mul
 guix shell qemu -- qemu-x86_64 -cpu max poly_mul
 Prime used for modulo operations: 127
 55 + 31 mod [-63,63] = -41
-Give first polynomial to multiply:
+Give first polynomial for the experiment:
 12 3 4 5
 Read polynomial: 5*x^3+4*x^2+3*x+12
-Give second polynomial to multiply:
+Give second polynomial for the experiment:
 11 1 2 3
 Read polynomial: 3*x^3+2*x^2+x+11
 Normal product of polynomials:
 15*x^6+22*x^5+22*x^4+101*x^3+71*x^2+45*x+132
+Normal sum of polynomials:
+8*x^3+6*x^2+4*x+23
 Give the degree m of X^m+1 polynomial to be used as divisor in the ring:
 7
 Product of polynomials in the ring:
 15*x^6+22*x^5+22*x^4-26*x^3-56*x^2+45*x+5
+Sum of polynomials in the ring:
+8*x^3+6*x^2+4*x+23
 ```
 
 Interestingly, only modulo operations in the latter range seem to be directly
diff --git a/poly_mul.c b/poly_mul.c
index db45bfd..dd86596 100644
--- a/poly_mul.c
+++ b/poly_mul.c
@@ -180,6 +180,18 @@ void poly_mul_in_ring(fmpz_poly_t res, fmpz_poly_t poly1, fmpz_poly_t poly2,
 	poly_to_ring(res, ctx);
 }
 
+void poly_add_in_ring(fmpz_poly_t res, fmpz_poly_t poly1, fmpz_poly_t poly2,
+		      poly_ring_ctx_t ctx) {
+	fmpz_poly_add(res, poly1, poly2);
+	poly_to_ring(res, ctx);
+}
+
+void poly_sub_in_ring(fmpz_poly_t res, fmpz_poly_t poly1, fmpz_poly_t poly2,
+		      poly_ring_ctx_t ctx) {
+	fmpz_poly_sub(res, poly1, poly2);
+	poly_to_ring(res, ctx);
+}
+
 int main(const int argc, const char* const* const argv) {
 	fmpz_t prime; /* integer for modulo operations */
 	mod_centered_0_ctx_t mod_ctx;
@@ -226,28 +238,34 @@ int main(const int argc, const char* const* const argv) {
 	} /* End of experiment 1 */
 
 	{ /* Experiment 2 */
-		fmpz_poly_t poly1, poly2, poly_prod;
+		fmpz_poly_t poly1, poly2, poly_computed;
 		slong divisor_degree;
 		poly_ring_ctx_t poly_ring_ctx;
 
-		printf("Give first polynomial to multiply:\n");
+		printf("Give first polynomial for the experiment:\n");
 		init_read_poly(poly1, stdin);
 
 		printf("Read polynomial: ");
 		fmpz_poly_print_pretty(poly1, "x");
 		putchar('\n');
 
-		printf("Give second polynomial to multiply:\n");
+		printf("Give second polynomial for the experiment:\n");
 		init_read_poly(poly2, stdin);
 
 		printf("Read polynomial: ");
 		fmpz_poly_print_pretty(poly2, "x");
 		putchar('\n');
 
+		fmpz_poly_init(poly_computed);
+
 		printf("Normal product of polynomials:\n");
-		fmpz_poly_init(poly_prod);
-		fmpz_poly_mul(poly_prod, poly1, poly2);
-		fmpz_poly_print_pretty(poly_prod, "x");
+		fmpz_poly_mul(poly_computed, poly1, poly2);
+		fmpz_poly_print_pretty(poly_computed, "x");
+		putchar('\n');
+
+		printf("Normal sum of polynomials:\n");
+		fmpz_poly_add(poly_computed, poly1, poly2);
+		fmpz_poly_print_pretty(poly_computed, "x");
 		putchar('\n');
 
 		printf("Give the degree m of X^m+1 polynomial to be used as ");
@@ -260,13 +278,18 @@ int main(const int argc, const char* const* const argv) {
 		poly_ring_ctx_init(poly_ring_ctx, mod_ctx, divisor_degree);
 
 		printf("Product of polynomials in the ring:\n");
-		poly_mul_in_ring(poly_prod, poly1, poly2, poly_ring_ctx);
-		fmpz_poly_print_pretty(poly_prod, "x");
+		poly_mul_in_ring(poly_computed, poly1, poly2, poly_ring_ctx);
+		fmpz_poly_print_pretty(poly_computed, "x");
+		putchar('\n');
+
+		printf("Sum of polynomials in the ring:\n");
+		poly_add_in_ring(poly_computed, poly1, poly2, poly_ring_ctx);
+		fmpz_poly_print_pretty(poly_computed, "x");
 		putchar('\n');
 
 		fmpz_poly_clear(poly1);
 		fmpz_poly_clear(poly2);
-		fmpz_poly_clear(poly_prod);
+		fmpz_poly_clear(poly_computed);
 
 		poly_ring_ctx_clear(poly_ring_ctx);
 	} /* End of experiment 2 */