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Task/Euler-method/Phix/euler-method.phix

@@ -0,0 +1,33 @@
+constant FMT = " %7.3f"
+
+procedure ivp_euler(integer f, atom y, integer step, integer end_t)
+integer t = 0;
+
+    printf(1, " Step %2d: ", step);
+    while t<=end_t do
+        if remainder(t,10)==0 then printf(1, FMT, y) end if
+        y += step * call_func(f,{t, y});
+        t += step
+    end while
+    printf(1, "\n");
+end procedure
+
+procedure analytic()
+    printf(1, "    Time: ");
+    for t = 0 to 100 by 10 do printf(1," %7g", t) end for
+    printf(1, "\nAnalytic: ");
+    for t = 0 to 100 by 10 do
+        printf(1, FMT, 20 + 80 * exp(-0.07 * t))
+    end for
+    printf(1,"\n");
+end procedure
+
+function cooling(atom /*t*/, atom temp)
+    return -0.07 * (temp - 20);
+end function
+constant r_cooling = routine_id("cooling")
+
+analytic();
+ivp_euler(r_cooling, 100, 2, 100);
+ivp_euler(r_cooling, 100, 5, 100);
+ivp_euler(r_cooling, 100, 10, 100);