Merge pull request #900 from RFigCon/main

Implementation of Train in Lua and D

00_Alternate_Languages/91_Train/D/README.md

@@ -0,0 +1,3 @@
+Original source downloaded from [Vintage Basic](http://www.vintage-basic.net/games.html).
+
+Conversion to [MiniScript](https://dlang.org).

00_Alternate_Languages/91_Train/D/train.d

@@ -0,0 +1,50 @@
+import std.stdio;
+import std.random : uniform;
+
+float abs(float num) {
+    if(num<0){
+        return num*-1;
+    }
+
+    return num;
+}
+
+void main() {
+    
+    writeln("\nTIME - SPEED DISTANCE EXERCISE");
+
+    bool keep_playing = true;
+    float error_margin = 5.0;
+
+    while(keep_playing){
+        int car_speed = uniform!"[]"(40,65);       //Random number between 40 and 65
+        int delta_time = uniform!"(]"(4,20);       //Between 5 and 20
+        int train_speed = uniform!"[)"(20,40);     //Between 20 and 39; This is the default if not specified: uniform(x,y)
+
+        writeln("\nA CAR TRAVELING AT ", car_speed, " MPH CAN MAKE A CERTAIN TRIP IN ", delta_time,
+                " HOURS LESS THAN A TRAIN TRAVELING AT ", train_speed, "MPH." );
+        
+        float input;
+        write("HOW LONG DOES THE TRIP TAKE BY CAR? ");
+        readf!"%f\n"(input);
+
+        float car_time = cast(float)delta_time * train_speed / (car_speed - train_speed);
+        int percent = cast(int)( abs(car_time-input) * 100 / car_time + .5);
+
+        if(percent > error_margin){
+            writeln("SORRY. YOU WERE OFF BY ", percent, " PERCENT.");
+        }else{
+            writeln("GOOD! ANSWER WITHIN ", percent, " PERCENT.");
+        }
+        writeln("CORRECT ANSWER IS ", car_time, " HOURS.");
+
+        string answer;
+        write("\nANOTHER PROBLEM (YES OR NO)? ");
+        readf!"%s\n"(answer);
+
+        if( !(answer == "YES" || answer == "Y" || answer == "yes" || answer == "y") ){
+            keep_playing = false;
+        }
+    }
+
+}