Data commit

Task/Arithmetic-geometric-mean/Modula-2/arithmetic-geometric-mean.mod2

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+MODULE AGM;
+FROM EXCEPTIONS IMPORT AllocateSource,ExceptionSource,GetMessage,RAISE;
+FROM LongConv IMPORT ValueReal;
+FROM LongMath IMPORT sqrt;
+FROM LongStr IMPORT RealToStr;
+FROM Terminal IMPORT ReadChar,Write,WriteString,WriteLn;
+
+VAR
+    TextWinExSrc : ExceptionSource;
+
+PROCEDURE ReadReal() : LONGREAL;
+VAR
+    buffer : ARRAY[0..63] OF CHAR;
+    i : CARDINAL;
+    c : CHAR;
+BEGIN
+    i := 0;
+
+    LOOP
+        c := ReadChar();
+        IF ((c >= '0') AND (c <= '9')) OR (c = '.') THEN
+            buffer[i] := c;
+            Write(c);
+            INC(i)
+        ELSE
+            WriteLn;
+            EXIT
+        END
+    END;
+
+    buffer[i] := 0C;
+    RETURN ValueReal(buffer)
+END ReadReal;
+
+PROCEDURE WriteReal(r : LONGREAL);
+VAR
+    buffer : ARRAY[0..63] OF CHAR;
+BEGIN
+    RealToStr(r, buffer);
+    WriteString(buffer)
+END WriteReal;
+
+PROCEDURE AGM(a,g : LONGREAL) : LONGREAL;
+CONST iota = 1.0E-16;
+VAR a1, g1 : LONGREAL;
+BEGIN
+    IF a * g < 0.0 THEN
+        RAISE(TextWinExSrc, 0, "arithmetic-geometric mean undefined when x*y<0")
+    END;
+
+    WHILE ABS(a - g) > iota DO
+        a1 := (a + g) / 2.0;
+        g1 := sqrt(a * g);
+
+        a := a1;
+        g := g1
+    END;
+
+    RETURN a
+END AGM;
+
+VAR
+    x, y, z: LONGREAL;
+BEGIN
+    WriteString("Enter two numbers: ");
+    x := ReadReal();
+    y := ReadReal();
+    WriteReal(AGM(x, y));
+    WriteLn
+END AGM.