Time for an 2014 update…

Task/Numeric-error-propagation/C/numeric-error-propagation.c

@@ -1,52 +1,75 @@
+#include <stdlib.h>
+#include <string.h>
 #include <stdio.h>
 #include <math.h>
 
-struct imprecise {
+typedef struct{
     double value;
     double delta;
-};
+}imprecise;
 
 #define SQR(x) ((x) * (x))
-struct imprecise imprecise_add(struct imprecise a, struct imprecise b)
+imprecise imprecise_add(imprecise a, imprecise b)
 {
-    struct imprecise ret;
+    imprecise ret;
     ret.value = a.value + b.value;
     ret.delta = sqrt(SQR(a.delta) + SQR(b.delta));
     return ret;
 }
 
-struct imprecise imprecise_mul(struct imprecise a, struct imprecise b)
+imprecise imprecise_mul(imprecise a, imprecise b)
 {
-    struct imprecise ret;
+    imprecise ret;
     ret.value = a.value * b.value;
     ret.delta = sqrt(SQR(a.value * b.delta) + SQR(b.value * a.delta));
     return ret;
 }
 
-struct imprecise imprecise_div(struct imprecise a, struct imprecise b)
+imprecise imprecise_div(imprecise a, imprecise b)
 {
-    struct imprecise ret;
+    imprecise ret;
     ret.value = a.value / b.value;
     ret.delta = sqrt(SQR(a.value * b.delta) + SQR(b.value * a.delta)) / SQR(b.value);
     return ret;
 }
 
-struct imprecise imprecise_pow(struct imprecise a, double c)
+imprecise imprecise_pow(imprecise a, double c)
 {
-    struct imprecise ret;
+    imprecise ret;
     ret.value = pow(a.value, c);
     ret.delta = fabs(ret.value * c * a.delta / a.value);
     return ret;
 }
 
+char* printImprecise(imprecise val)
+{
+	char principal[30],error[30],*string,sign[2];
+	sign[0] = 241;    /* ASCII code for ±, technical notation for denoting errors */
+	sign[1] = 00;
+	
+	sprintf(principal,"%f",val.value);
+	sprintf(error,"%f",val.delta);
+	
+	string = (char*)malloc((strlen(principal)+1+strlen(error)+1)*sizeof(char));
+	
+	strcpy(string,principal);
+	strcat(string,sign);
+	strcat(string,error);
+	
+	return string;
+}
+
 int main(void) {
-    struct imprecise x1 = {100, 1.1};
-    struct imprecise y1 = {50, 1.2};
-    struct imprecise x2 = {-200, 2.2};
-    struct imprecise y2 = {-100, 2.3};
-    struct imprecise d;
+    imprecise x1 = {100, 1.1};
+    imprecise y1 = {50, 1.2};
+    imprecise x2 = {-200, 2.2};
+    imprecise y2 = {-100, 2.3};
+    imprecise d;
 
     d = imprecise_pow(imprecise_add(imprecise_pow(imprecise_add(x1, x2), 2),imprecise_pow(imprecise_add(y1, y2), 2)), 0.5);
-    printf("d = %f \\pm %f\n", d.value, d.delta);
+    printf("Distance, d, between the following points :");
+    printf("\n( x1, y1) = ( %s, %s)",printImprecise(x1),printImprecise(y1));
+    printf("\n( x2, y2) = ( %s, %s)",printImprecise(x2),printImprecise(y2));
+    printf("\nis d = %s", printImprecise(d));
     return 0;
 }

Task/Numeric-error-propagation/PicoLisp/numeric-error-propagation-1.l

@@ -91,4 +91,4 @@
       (pack
          (round (car N) 10)
          " ± "
-         (round (sqrt (* 1.0 (cdr N))) 8) ) ) )
+         (round (sqrt (cdr N) 1.0) 8) ) ) )