Phase 2: variables, arrays, program execution, and control flow

Add variable storage (scalar and array), program line storage with
RUN/LIST/NEW, and full control flow: FOR/NEXT, GOTO, GOSUB/RETURN,
IF/THEN/ELSE, WHILE/WEND, ON GOTO/GOSUB, DATA/READ/RESTORE.

New modules: interp.c (1445 lines - execution loop and statement
dispatcher), vars.c, arrays.c, input.c. Version bumped to 0.2.0.
16 test programs pass including Leibniz pi and prime sieve.

tests/programs/arrays.bas

@@ -0,0 +1,15 @@
+10 REM Array test
+20 DIM A(10), B$(5)
+30 FOR I = 0 TO 10
+40 A(I) = I * I
+50 NEXT I
+60 FOR I = 0 TO 10
+70 PRINT A(I);
+80 NEXT I
+90 PRINT
+100 B$(0) = "Zero"
+110 B$(1) = "One"
+120 B$(2) = "Two"
+130 FOR I = 0 TO 2
+140 PRINT B$(I)
+150 NEXT I

tests/programs/control_flow.bas

@@ -0,0 +1,12 @@
+10 REM Control flow: GOTO, IF, FOR, GOSUB combined
+20 GOTO 40
+30 PRINT "SKIP THIS"
+40 PRINT "Start"
+50 FOR I = 1 TO 3
+60 IF I = 2 THEN GOSUB 200
+70 PRINT "I ="; I
+80 NEXT I
+90 PRINT "End"
+100 END
+200 PRINT "  (subroutine called)";
+210 RETURN

tests/programs/data_read.bas

@@ -0,0 +1,9 @@
+10 REM DATA/READ test
+20 DATA 10, 20, 30, "hello", "world"
+30 READ A, B, C
+40 PRINT A; B; C
+50 READ D$, E$
+60 PRINT D$; " "; E$
+70 RESTORE
+80 READ X
+90 PRINT "After RESTORE:"; X

tests/programs/def_fn.bas

@@ -0,0 +1,6 @@
+10 REM DEF FN test
+20 DEF FN SQ(X) = X * X
+30 DEF FN CU(X) = X * X * X
+40 PRINT "5 squared ="; FN SQ(5)
+50 PRINT "3 cubed ="; FN CU(3)
+60 PRINT "Sum ="; FN SQ(3) + FN CU(2)

tests/programs/for_next.bas

@@ -0,0 +1,10 @@
+10 REM FOR/NEXT test
+20 FOR I = 1 TO 5
+30 PRINT I;
+40 NEXT I
+50 PRINT
+60 REM FOR with STEP
+70 FOR I = 10 TO 0 STEP -2
+80 PRINT I;
+90 NEXT I
+100 PRINT

tests/programs/gosub.bas

@@ -0,0 +1,15 @@
+10 REM GOSUB/RETURN test
+20 PRINT "Main program"
+30 GOSUB 100
+40 PRINT "Back from first sub"
+50 GOSUB 200
+60 PRINT "Back from second sub"
+70 END
+100 REM First subroutine
+110 PRINT "In first subroutine"
+120 GOSUB 200
+130 PRINT "Back in first sub"
+140 RETURN
+200 REM Second subroutine
+210 PRINT "In second subroutine"
+220 RETURN

tests/programs/if_then_else.bas

@@ -0,0 +1,8 @@
+10 REM IF/THEN/ELSE test
+20 X = 5
+30 IF X > 3 THEN PRINT "X > 3" ELSE PRINT "X <= 3"
+40 IF X < 3 THEN PRINT "X < 3" ELSE PRINT "X >= 3"
+50 REM IF with GOTO
+60 IF X = 5 THEN GOTO 80
+70 PRINT "Should not print"
+80 PRINT "Jumped to 80"

tests/programs/leibniz.bas

@@ -0,0 +1,6 @@
+10 REM Leibniz formula for pi
+20 S = 0
+30 FOR I = 0 TO 999
+40 S = S + (-1)^I / (2*I+1)
+50 NEXT I
+60 PRINT "Pi approx:"; 4*S

tests/programs/nested_for.bas

@@ -0,0 +1,7 @@
+10 REM Nested FOR loops - multiplication table
+20 FOR I = 1 TO 5
+30 FOR J = 1 TO 5
+40 PRINT I*J;
+50 NEXT J
+60 PRINT
+70 NEXT I

tests/programs/on_goto.bas

@@ -0,0 +1,11 @@
+10 REM ON GOTO/GOSUB test
+20 FOR I = 1 TO 3
+30 ON I GOTO 100, 200, 300
+40 NEXT I
+50 END
+100 PRINT "Branch 1"
+110 GOTO 40
+200 PRINT "Branch 2"
+210 GOTO 40
+300 PRINT "Branch 3"
+310 GOTO 40

tests/programs/prime_sieve.bas

@@ -0,0 +1,18 @@
+10 REM Sieve of Eratosthenes
+20 N = 100
+30 DIM P(100)
+40 FOR I = 2 TO N
+50 P(I) = 1
+60 NEXT I
+70 FOR I = 2 TO SQR(N)
+80 IF P(I) = 0 THEN GOTO 120
+90 FOR J = I*2 TO N STEP I
+100 P(J) = 0
+110 NEXT J
+120 NEXT I
+130 C = 0
+140 FOR I = 2 TO N
+150 IF P(I) = 1 THEN PRINT I; : C = C + 1
+160 NEXT I
+170 PRINT
+180 PRINT C; "primes found"

tests/programs/variables.bas

@@ -0,0 +1,11 @@
+10 REM Variable types test
+20 A% = 42
+30 B! = 3.14
+40 C# = 2.718281828
+50 D$ = "Hello"
+60 PRINT A%; B!; C#
+70 PRINT D$
+80 REM DEFINT test
+90 DEFINT X-Z
+100 X = 7.9
+110 PRINT X

tests/programs/while_wend.bas

@@ -0,0 +1,8 @@
+10 REM WHILE/WEND test
+20 X = 1
+30 WHILE X <= 10
+40 IF X MOD 2 = 0 THEN PRINT X;
+50 X = X + 1
+60 WEND
+70 PRINT
+80 PRINT "Done"