tasks a-s

Task/Resistor-mesh/BBC-BASIC/resistor-mesh.bbc

@@ -0,0 +1,31 @@
+      INSTALL @lib$+"ARRAYLIB"
+      *FLOAT 64
+      @% = &F0F
+
+      PRINT "Resistance = "; FNresistormesh(10, 10, 1, 1, 7, 6) " ohms"
+      END
+
+      DEF FNresistormesh(ni%, nj%, ai%, aj%, bi%, bj%)
+      LOCAL c%, i%, j%, k%, n%, A(), B()
+      n% = ni% * nj%
+      DIM A(n%-1, n%-1), B(n%-1, 0)
+      FOR i% = 0 TO ni%-1
+        FOR j% = 0 TO nj%-1
+          k% = i% * nj% + j%
+          IF i% = ai% AND j% = aj% THEN
+            A(k%, k%) = 1
+          ELSE
+            c% = 0
+            IF (i% + 1) < ni% c% += 1 : A(k%, k% + nj%) = -1
+            IF i% > 0         c% += 1 : A(k%, k% - nj%) = -1
+            IF (j% + 1) < nj% c% += 1 : A(k%, k% + 1)   = -1
+            IF j% > 0         c% += 1 : A(k%, k% - 1)   = -1
+            A(k%, k%) = c%
+          ENDIF
+        NEXT
+      NEXT
+      k% = bi% * nj% + bj%
+      B(k%, 0) = 1
+      PROC_invert(A())
+      B() = A().B()
+      = B(k%, 0)