3 files changed, 35 insertions, 1 deletions
diff --git a/Makefile b/Makefile
index a4b2611..3446aa7 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,7 @@ HEAD=
 OBJ=${DEPS:.c=.o}
 
 LIB=las.a
-LDEPS=bullet_loan.c
+LDEPS=bullet_loan.c straight_line_loan.c
 LHEAD=contract.h loans.h
 LOBJ=${LDEPS:.c=.o}
 
diff --git a/loans.h b/loans.h
index 8d99de7..8613028 100644
--- a/loans.h
+++ b/loans.h
@@ -6,3 +6,8 @@
 contract *bullet_init(int n, int d, float r, float P);
 float bullet_update(contract *);
 void bullet_free(contract *c);
+
+/**** STRAIGHT LINE ****/
+contract *sl_init(int n, int d, float r, float P);
+float sl_update(contract *);
+void sl_free(contract *);
diff --git a/straight_line_loan.c b/straight_line_loan.c
new file mode 100644
index 0000000..0d25247
--- /dev/null
+++ b/straight_line_loan.c
@@ -0,0 +1,29 @@
+#include "loans.h"
+
+contract *sl_init(int n, int d, float r, float P) {
+	if ((n < 0)) return NULL;
+	if ((d > n)||(d < 0)) return NULL;
+	contract *c = (contract *)calloc(1, sizeof(contract));
+	c->n = (unsigned int)n;
+	c->d = (unsigned int)d;
+	c->r = r;
+	c->P = P;
+	c->D = P/(float)n;
+
+	return c;
+}
+
+float sl_update(contract *c) {
+	if (c->k > c->n)
+		return 0.0f;
+	c->k++;
+	c->I = c->r * c->P;
+	c->P = c->P - c->D;
+	c->A = c->D + c->I;
+
+	return c->A;
+}
+
+void sl_free(contract *c) {
+	free(c);
+}