added delays to loans

1 files changed, 11 insertions, 5 deletions

diff --git a/straight_line_loan.c b/straight_line_loan.c
index 73ba859..df86dcc 100644
--- a/straight_line_loan.c
+++ b/straight_line_loan.c
@@ -2,13 +2,12 @@
 
 contract *sl_init(int n, int d, float r, float P) {
 	if ((n < 0)) return NULL;
-	if ((d > n)||(d < 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;
 }
@@ -16,11 +15,18 @@ contract *sl_init(int n, int d, float r, float P) {
 float sl_update(contract *c) {
 	if (c->k > c->n)
 		return 0.0f;
+
+	if (c->k == c->d) c->D = c->P/(float)(c->n - c->k);
 	c->k++;
 	c->I = c->r * c->P;
-	c->P = c->P - c->D;
-	c->A = c->D + c->I;
-	/* c->D is fixed ! */
+
+	if (c->k <= c->d)
+		c->P += c->I;
+	else {
+		c->P = c->P - c->D;
+		c->A = c->D + c->I;
+		/* c->D is fixed ! */
+	}
 
 	return c->A;
 }