Initial data commit

Task/Numerical-integration/Pascal/numerical-integration.pas

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+function RectLeft(function f(x: real): real; xl, xr: real): real;
+ begin
+  RectLeft := f(xl)
+ end;
+
+function RectMid(function f(x: real): real; xl, xr: real) : real;
+ begin
+  RectMid := f((xl+xr)/2)
+ end;
+
+function RectRight(function f(x: real): real; xl, xr: real): real;
+ begin
+  RectRight := f(xr)
+ end;
+
+function Trapezium(function f(x: real): real; xl, xr: real): real;
+ begin
+  Trapezium := (f(xl) + f(xr))/2
+ end;
+
+function Simpson(function f(x: real): real; xl, xr: real): real;
+ begin
+  Simpson := (f(xl) + 4*f((xl+xr)/2) + f(xr))/6
+ end;
+
+function integrate(function method(function f(x: real): real; xl, xr: real): real;
+                   function f(x: real): real;
+                   a, b: real;
+                   n: integer);
+ var
+  integral, h: real;
+  k: integer;
+ begin
+  integral := 0;
+  h := (b-a)/n;
+  for k := 0 to n-1 do
+   begin
+    integral := integral + method(f, a + k*h, a + (k+1)*h)
+   end;
+  integrate := integral
+ end;