OPTION BASE [0 | 1]
10 OPTION BASE 0 DIM name$(4) 20 FOR i = 0 TO 4 - INPUT 'Enter a name': name$(i) , PRINT i; ' Hello, '; name$(i) NEXT i 30 END RNH Enter a name? June 0 Hello, June Enter a name? Tony 1 Hello, Tony Enter a name? Sandy 2 Hello, Sandy Enter a name? Carl 3 Hello, Carl Enter a name? Liz 4 Hello, Liz
B Use OPTION BASE to set the default low bound for arrays to K suit your needs. You have the option of starting the array with element O or element 1.
G When no low bound is specified for a dimension, the default is 1. The G OPTION BASE statement lets you specify a default low bound of 0 or 1. J When any following DIM or REDIM statements are executed, INTOUCH defaults & the low bound to 0 or 1 as specified.
G A LOOP is a section of code that can be repeated. There are two types of loops.
= A FOR loop is used when you need to repeat a block of code a A specific number of times. FOR loops are also good when you need C to know how many times the loop was executed. You might use a FOR B loop if you need to input 10 similar data items. You might use a C FOR loop as a counter--say to count from 1 to 1000, or if you need = to make calculations from each of the 10 data items entered.
A DO loops are used when you need to execute a block of code until D a specific condition is met. For instance, you might use a DO loop E if you need to enter numbers until a 0 is entered. Or you might use D DO loops if you need to do calculations until two numbers match, or C if you need to continue a process until either the user chooses to ) stop or until a final result is reached.
D Loops are constructs. They are created by using several statements B which can only be used in conjunction with one another (FOR/NEXT, E DO/LOOP). The statements which make up the constructs are described together.
@ FOR index_var = num_expr1 TO num_expr2 [STEP num_expr3] . --- # --- block of code --- NEXT index_var
10 DIM name$(4) 20 FOR j = 1 TO 4 + INPUT 'Enter name': name$(j) % PRINT j; ' '; name$(j) NEXT j 30 PRINT 'Finished' $ PRINT 'Final value:'; j 40 END RNH Enter name? Jack 1 Jack Enter name? Tom 2 Tom Enter name? Sue 3 Sue Enter name? Toby 4 Toby Finished Final value: 5
> Use the FOR loop to execute a block of code a specific K number of times. You can use this construct to repeat a section of code a certain number of times.
I In the above example, the INPUT and PRINT statements make up the body of J the loop. This block of code is executed each time the loop is repeated. A (For clarity, the body of the loop is indented two spaces.) The 9 FOR statement marks the beginning of the loop and A determines how many times the loop is repeated. The NEXT % statement marks the end of the loop.
index variable | V 6 FOR J = 1 TO 4 <-- limit expression ^ | initial expression
General Information
A The index variable keeps track of how many times the loop @ has been executed. The initial expression is the number @ INTOUCH begins counting at. The limit expression is the I number INTOUCH stops counting at. In the example, INTOUCH counts from 1 ' to 4, so the loop executes four times.
H When INTOUCH runs the example program, it executes the loop four times. J The first time the FOR statement is executed, the variable J is set to 1. N INTOUCH executes the body of the loop. Since J = 1, INTOUCH inputs NAME$(1), Jack, and prints NAME$(J).
RNH % J = 1 Enter name? Jack 1 Jack
H When INTOUCH reaches the NEXT J, it adds one to J and jumps back to the K beginning of the loop. J is now 2. INTOUCH checks to see if J is greater G than 4. Since J isn't greater than 4, INTOUCH repeats the loop. When L INTOUCH executes the loop for the last time, it jumps back to the beginning ? of the loop and checks to see if J is greater than 4. Since J C is greater than 4, INTOUCH jumps to the statement following F the NEXT J (PRINT 'Finished') and continues normal program execution.
RNH % J = 1 Enter name? Jack 1 Jack $ J = 2 Enter name? Tom 2 Tom $ J = 3 Enter name? Sue 3 Sue % J = 4 Enter name? Toby 4 Toby Finished # Final value: 5<
F By default, when a FOR loop is executed, INTOUCH increments the index J variable by one. The increment can be changed with the STEP option. The 5 format of the FOR statement with the STEP option is:
> FOR index_var = num_expr1 TO num_expr2 STEP num_expr3 --- --- block of code --- NEXT index_var
F num_expr3 is a a numeric expression specifying the increment. K Each time the FOR statement is executed, INTOUCH adds the increment to the J index variable. INTOUCH stops executing the loop when the index variable is greater than the limit.
10 DIM name$(4) " 20 FOR j = 1 TO 4 STEP 3 + INPUT 'Enter name': name$(j) % PRINT j; ' '; name$(j) NEXT j 30 PRINT 'Finished' $ PRINT 'Final value:'; j 40 END RNH Enter name? Fred 1 Fred Enter name? John 4 John Finished Final value: 7:
H FOR loops can be nested. A nested loop is a loop which begins and ends A inside of another loop. Loops cannot overlap. The inner : loop must begin and end completely within the outer loop.
) start of 10 DIM name$(4) + outer loop --- 20 FOR j = 1 TO 4 - INPUT name$(j) - FOR k = 1 TO j 9 inner loop --- PRINT name$(k); ' '; % NEXT k $ end of PRINT # outer loop --- NEXT j - 30 PRINT 'Finished' 40 END RNH ? FRED FRED ? JOHN # FRED JOHN ? MARY ) FRED JOHN MARY ? KATE / FRED JOHN MARY KATE ! Finished5
EXIT FOR
10 FOR i = 1 TO 5 / INPUT 'Your name, please': name$ ( IF _EXIT THEN EXIT FOR % PRINT 'Hello, '; name$ NEXT i 20 PRINT 'Finished' 30 END RNH ! Your name, please? James Hello, James " Your name, please? Marian Hello, Marian Your name, please? exit
- Use EXIT FOR to exit from a FOR loop.
M When INTOUCH executes an EXIT FOR statement, it jumps to the first statement M following the matching NEXT statement. EXIT FOR can only be used within FOR E loops. If EXIT FOR is used within a nested loop, INTOUCH exits the innermost loop.
REPEAT FOR
10 FOR i = 1 TO 3 PRINT i / INPUT 'Your name, please': name$ / IF name$ = '' THEN REPEAT FOR % PRINT 'Hello, '; name$ NEXT i 20 END RNH 1 " Your name, please? George Hello, George 2 Your name, please? 2 Your name, please? Sam Hello, Sam 3 Your name, please? Tom Hello, Tom
> To repeat a FOR loop without incrementing the index variable.
= REPEAT FOR repeats all or part of the body of a loop. M REPEAT FOR can only be used in FOR loops. When INTOUCH executes REPEAT FOR, = it jumps to the first statement following the FOR statement.
@ If REPEAT FOR is used within a nested loop, INTOUCH repeats the innermost loop.
( 10 FOR i = 1 TO 10 ) FOR j = 1 to 5 $ INTOUCH will PRINT j = repeat this INPUT 'Your name, please': name$ = inner loop -------- IF name$ = '' THEN REPEAT FOR 3 PRINT 'Hello, '; name$ ! NEXT j E PRINT 'We now have'; i; 'set(s) of names.' NEXT i 20 END
ITERATE FOR
10 FOR i = 1 TO 3 PRINT i 0 INPUT 'Your name, please' : name$ 4 IF name$ = 'SKIP' THEN ITERATE FOR % PRINT 'Hello, '; name$ NEXT i 20 END RNH 1 Your name, please? Toby Hello, Toby 2 Your name, please? SKIP 3 Your name, please? Sam Hello, Sam
To skip code processing.
? When INTOUCH executes ITERATE FOR, it jumps to the NEXT J statement. Any statements between the ITERATE FOR and the NEXT statement will be skipped.
N If ITERATE FOR is used in a nested loop, INTOUCH iterates the innermost loop.
& 10 FOR i = 1 TO 10 ' FOR j = 1 TO 5 " PRINT j ; INPUT 'Your name, please': name$ = INTOUCH will IF name$ = 'SKIP' THEN ITERATE FOR 1 skip this line ----- PRINT 'Hello, '; name$ NEXT j C PRINT 'We now have'; i; 'sets of name(s).' NEXT i 20 END
% DO [WHILE expr | UNTIL expr] --- # --- block of code --- ' LOOP [WHILE expr | UNTIL expr]
10 a = 3 20 DO UNTIL a = 0 / INPUT 'Your name, please': name$ % PRINT 'Hello, '; name$ a = a - 1 LOOP 30 END RNH Your name, please? Sam Hello, Sam Your name, please? Sue Hello, Sue Your name, please? Bart Hello, Bart
> Use a DO LOOP to execute a block of code repeatedly -- $ until a specified condition is met.
5 The simplest type of DO LOOP is an infinite DO LOOP:
10 DO 0 INPUT 'Your name, please' : name$ % PRINT 'Hello, '; name$ LOOP 20 END
I In the above example, the INPUT and PRINT statements make up the body of J the loop. This block of code is executed each time the loop is repeated. 6 DO begins the loop. LOOP marks the end J of the loop. When INTOUCH reaches the LOOP statement it jumps back to DO and executes the loop again.
O The Ctrl/C command can be used to break out of an infinite DO loop. 2 (For a full description of Ctrl/C, see Interrupting the Program.)
A DO loops can be nested. Loops cannot overlap. The inner M loop must be completely within the DO and LOOP statements of the outer loop.
start of outer loop --- 10 DO $ a = 5 - DO UNTIL a = 0 : / INPUT 'Your name' : name$ 7 inner loop PRINT 'Hello, '; name$ * \ a = a - 1 # LOOP 7 end of PRINT 'Done with a loop' ! outer loop --- LOOP 20 END
@ DO loops can be made conditional with WHILE and UNTIL options. A WHILE and UNTIL set up a condition. The loop is executed if the condition is met.
D 11.2.1 WHILE and UNTIL Options
WHILE cond_expr
10 a = 3 20 DO / INPUT 'Your name, please': name$ % PRINT 'Hello, '; name$ a = a - 1 LOOP WHILE a > 0 30 PRINT 'Finished' 40 END RNH Your name, please? FRED Hello, FRED Your name, please? JOHN Hello, JOHN Your name, please? KATE Hello, KATE Finished
E cond_expr is a conditional expression. When INTOUCH executes A the WHILE option, it evaluates the conditional expression 7 as either TRUE (1) or FALSE (0). If the H expression is TRUE, the condition is met and INTOUCH executes the loop. I INTOUCH continues executing the loop until the expression becomes FALSE. L When the expression becomes FALSE, the condition is not met. INTOUCH stops > executing the loop and jumps to the statement following LOOP.
UNTIL cond_expr
10 a = 3 DO UNTIL a = 0 / INPUT 'Your name, please': name$ % PRINT 'Hello, '; name$ a = a - 1 LOOP PRINT 'Finished' 20 END RNH Your name, please? FRED Hello, FRED Your name, please? JOHN Hello, JOHN Your name, please? KATE Hello, KATE Finished
E cond_expr is a conditional expression. When INTOUCH executes A the UNTIL option, it evaluates the conditional expression 7 as either TRUE (1) or FALSE (0). If the M expression is FALSE, INTOUCH executes the loop. INTOUCH continues executing I the loop until the expression becomes TRUE. When the expression becomes L TRUE, INTOUCH stops executing the loop and jumps to the statement following LOOP.
%
J WHILE and UNTIL can be attached to the DO and/or to the LOOP statements. J Whenever INTOUCH encounters a WHILE or UNTIL clause, it checks whether to D execute the loop. So, where the WHILE and UNTIL clauses are placed $ affects the execution of the loop.
J If a WHILE or UNTIL is attached to the DO statement, INTOUCH first checks J to see whether the condition is TRUE or FALSE before it executes the loop J (again). In the case of a WHILE statement, if the condition is still met H (i.e. is TRUE), INTOUCH executes the loop. If the condition is not met I (i.e. is FALSE or is no longer TRUE), INTOUCH does not execute the loop.
E In the case of an UNTIL statement, if the condition has not been met B (or is still FALSE), INTOUCH executes the loop once more. If the D condition has been met (i.e. is TRUE), INTOUCH does not execute the loop again.
A WHILE and UNTIL options can be placed at both ends of the loop. J INTOUCH evaluates each expression in turn. When it finds that one of the I conditions has or has not been met (depending upon whether it is a WHILE G or UNTIL clause), INTOUCH stops executing the loop. For example, when G the following program runs, INTOUCH executes the loop until A equals 5 or the user enters EXIT.
10 DIM name$(4) a = 1 20 DO UNTIL a = 5 3 INPUT 'Your name, please' : name$(a) a = a + 1 ! LOOP WHILE NOT _EXIT 30 PRINT 'Finished' 40 END4
EXIT DO
10 DO 0 INPUT 'Your name, please' : name$ ' IF _EXIT THEN EXIT DO % PRINT 'Hello, '; name$ LOOP 20 PRINT 'Finished' 30 END RNH Your name, please? Fred Hello, Fred Your name, please? exit Finished
+ Use EXIT DO to exit from a DO loop.
B When INTOUCH executes an EXIT DO statement, it jumps to the first A statement following the LOOP or END DO statement. If EXIT DO is = used within a nested loop, INTOUCH exits the innermost loop.
A DO...END DO is a single iteration loop. The code between G DO and END DO is processed only once unless conditional code specifies exiting or repeating the DO.
REPEAT DO
10 DO / INPUT 'Your name, please': name$ ' IF _EXIT THEN EXIT DO . IF name$ = '' THEN REPEAT DO % PRINT 'Hello, '; name$ LOOP 20 END RNH Your name, please? Fred Hello, Fred Your name, please? Your name, please? exit
2 Use REPEAT DO to repeat part of a DO loop.
C REPEAT DO repeats all or part of the body of a loop. When INTOUCH B executes REPEAT DO, it jumps to the first statement following the DO statement.
? If REPEAT DO is used within a nested loop, INTOUCH repeats the innermost loop.
3 10 DO * i = i + 1 * DO C INTOUCH will repeat INPUT 'Your name, please': name$ ; this inner loop -------- IF _EXIT THEN EXIT DO B IF name$ = '' THEN REPEAT DO 9 PRINT 'Hello, '; name$ % LOOP K PRINT 'We now have'; i; 'set(s) of names.' # LOOP " 20 END
ITERATE DO
10 DO / INPUT 'Your name, please': name$ ' IF _EXIT THEN EXIT DO 3 IF name$ = 'SKIP' THEN ITERATE DO % PRINT 'Hello, '; name$ LOOP 20 END RNH Your name, please? FRED Hello, Fred Your name, please? SKIP Your name, please? EXIT
C Use ITERATE DO to repeat a loop, skipping part of the loop.
J ITERATE DO repeats a loop. When INTOUCH executes ITERATE DO, it jumps to I the LOOP or END DO statement. Any statements between the ITERATE DO and 3 the end of the DO block statement will be skipped.
G If ITERATE DO is used in a nested loop, INTOUCH iterates the innermost loop.
% 10 DO 2 LET i = i + 1 ' DO H INTOUCH will INPUT 'Your name, please' : name$ K iterate this inner loop ---- IF name$ = 'SKIP' THEN ITERATE DO ? IF _EXIT THEN EXIT DO = PRINT 'Hello, '; name$ ) LOOP O PRINT 'We now have'; i; 'set(s) of names.' ' LOOP & 20 END
EXECUTE str_expr
4 10 INPUT 'Enter a video attribute': video$ + 20 z$ = 'print ' + video$ + & @ ': "This will be printed using ' + video$ + '"' 30 EXECUTE z$ 40 END RNH & Enter a video attribute? bold . This will be printed using bold
10 nbr_fields = 5 # 20 DIM check$(nbr_fields) 30 check$(1) = & 'DO \' & ; + ' IF len(ans$) <> 9 THEN \' & E + ' MESSAGE ERROR : "SSN must be 9 digits" \' & & + ' EXIT DO \' & # + ' END IF \' & @ + ' IF not valid(ans$, "number") THEN \' & D + ' MESSAGE ERROR : "SSN must be numeric" \' & & + ' EXIT DO \' & # + ' END IF \' & 1 + ' PRINT "SSN is valid" \' & + 'END DO' 40 field_nbr = 1 50 INPUT 'SSN' : ans$ & 60 EXECUTE check$(field_nbr) 70 END RNH SSN? 123456789 SSN is valid
; EXECUTE allows you to incorporate new code into the D program at run time. It is mostly used for generalized procedures, utilities, and tools.
D A string is built which contains the INTOUCH statements to execute. @ Multiple INTOUCH statements are separated by either a line feed ( character (chr$(10) or a "\" character.
D When an EXECUTE statement is encountered, INTOUCH compiles the code > contained in the string and then runs that code. All program ? variables are available to the executed code and any variables B established by the executed code are available to the rest of the program.
B An executed string is only compiled once. When a string has been @ compiled, the code contained within that string is processed as & efficiently as the main program code.
? The EXECUTE statement makes the coding of powerful generalized routines very easy.
@ Conditionals are constructs which allow you to execute specific C blocks of code depending on one or more conditions. For instance, E suppose you are doing a tax program. You need to use the EZ form if E certain conditions are met, the short form if others are met and the C long form otherwise. You can use a conditional to determine which form to use.
F There are two types of conditionals, IF and SELECT. The IF construct F is useful when you need to check one or more conditions and execute a D different block of code depending on the result. For instance, say C that you need to print one statement if the user is male and under A 20, another if the user is male and between 20 and 40, and still A another if the user is male and over 40. The IF construct works well in this kind of situation.
A The SELECT CASE construct is useful when you need to compare one B main expression with several values and execute a different block D of code for each possible match. For instance, suppose that in the G tax program we mentioned before, you need to execute a different block B of code depending on the tax bracket the user is in. SELECT CASE ? would let you compare a main expression---BRACKET with all the 8 possible tax brackets (10000-15000, 15000-25000, etc.).
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