Further bug fix 1990/theorem

If not enough args were specified it would segfault.

It also now uses fgets() instead of gets().

1990/theorem/README.md

@@ -12,8 +12,13 @@
         make all
 
 [Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed some segfaults
-under modern (and in some cases earlier) systems with this entry. Thank you Cody
-for your assistance!
+under modern (and in some cases earlier) systems with this entry. He also fixed
+a segfault if not enough args are used. Originally we noted that the 4 trailing
+args '0 0 0 0' were required on systems that dump core when NULL is dereferenced
+but this problem showed itself in modern systems even with the 4 '0 0 0 0'. To
+make this easier for users Cody also kindly fixed this problem. Finally he
+changed this program to use `fgets()` not `gets()` to make it safer. Thank you
+Cody for your assistance!
 
 [Yusuke Endoh](/winners.html#Yusuke_Endoh) pointed out that `atof` nowadays
 needs `#include <stdlib.h>` which was used in order to get this to work
@@ -22,7 +27,7 @@ initially. Thank you Yusuke!
 
 ## To run:
 
-	./mariano expression x1 x2 h y1
+	./theorem expression x1 x2 h y1
 
 where:
 
@@ -35,7 +40,7 @@ where:
 
 ## Try:
 
-	./mariano y 0 1 0.1 1
+	./theorem y 0 1 0.1 1
 
 
 
@@ -44,7 +49,7 @@ where:
 The program's source implements four functions, all from the
 same source file!
 
-When you compile mariano.c as is and run with 5 args, it numerically
+When you compile theorem.c as is and run with 5 args, it numerically
 solves the equation y'=f(x,y), with a step size of h, over the interval 
 x=[x1,x2], with the initial condition of y(x1)=y1.
 
@@ -59,14 +64,14 @@ left to right.  (i.e., parenthesis aren't supported).
 
 Try running the program with the following args:
 
-	./mariano y 0 1 0.1 1
-	./mariano 1/x 1 2 0.1 0
-	./mariano 'x^2/y+x' 0 1 0.1 6
+	./theorem y 0 1 0.1 1
+	./theorem 1/x 1 2 0.1 0
+	./theorem 'x^2/y+x' 0 1 0.1 6
 
 But wait, there is more!  You also get, free of charge, a 
 reversing filter!  Try:
 
-	./mariano -r 0 0 0 0 < mariano.c > sorter.c
+	./theorem -r 0 0 0 0 < theorem.c > sorter.c
 
 Still not impressed?  The author throws in for free, a 
 sort program! Try:
@@ -78,12 +83,12 @@ This program is safe for home use as well.  The author has
 included a safety feature in case you misplace the original
 program source:
 
-    ./sorter -r 0 0 0 0 < sorter.c > mariano_bkp.c
+    ./sorter -r 0 0 0 0 < sorter.c > theorem_bkp.c
 
 And finally, as a special offer to users of this entry,
 the author provides a Fibonacci sequence generator!  Try:
 
-    ./sorter 0 0 0 0 < mariano.c > fibonacci.c
+    ./sorter 0 0 0 0 < theorem.c > fibonacci.c
     cc fibonacci.c -o fibonacci
     ./fibonacci 1 1
     ./fibonacci 2 1
@@ -95,10 +100,6 @@ When this program was first shown at the 1990 Summer Usenix
 conference, it received a standing ovation; a first for
 a contest entry.
 
-Originally we noted that the 4 trailing args '0 0 0 0' were required on systems
-that dump core when NULL is dereferenced but this problem showed itself in
-modern systems even with the 4 '0 0 0 0'. To make this easier for users Cody
-Boone Ferguson kindly fixed this problem.
 
 
 ## Author's comments

1990/theorem/theorem.c

@@ -24,6 +24,7 @@ w(g,R,u)float*g,u;char R;
 /**/{int b,f;A=atoi(++a);b=atoi(++a);while((f=A+b)<15000){printf("%d\n",f);A=b;b=f;}}
 main(A,a)int A;char*a[];
 o o
+if (a[1]==NULL||a[2]==NULL||a[3]==NULL||a[4]==NULL||a[5]==NULL) return 1;
 if(!strcmp(*++a,"-r"))S();
 D=atof(*++a);
 T=atof(*++a);
@@ -78,12 +79,12 @@ return O;
 for(j=0;j<n;puts(j++[m]));
 e("",O,O,a);
 n=j-(O=1);
-while(gets(j++[m]));
+while(fgets(j++[m],500,stdin));
 if(!strcmp(++a,"-r"))S();
 C
 /**/main(A,a)int A;char*a[];
 Y
-S(){while(gets(b++[m]));for(b--;b--;puts(b[m]));}
+S(){while(fgets(b++[m],500,stdin));for(b--;b--;puts(b[m]));}
 char*f,m[500][99],R,v[99];
 int b,W,n,i,j,z;
 float Q,G,D,M,T,O,B,U,V,N,e();