5 IF cond_expr THEN statement [ELSE statement] or IF cond_expr1 THEN --- --- block of code --- [ELSEIF cond_expr2 THEN --- --- block of code --- ...] [ELSE --- --- block of code --- ] END IF
1 10 INPUT PROMPT 'Enter your age: ': age 2 INPUT PROMPT 'Enter your sex: ': sex$ F 20 IF UCASE$(sex$[1:1]) = 'M' THEN GOTO done ELSE PRINT " 30 IF age < 20 THEN + PRINT 'Please go to line A.' 8 ELSEIF age > 19 AND age < 40 THEN + PRINT 'Please go to line B.' ELSE + PRINT 'Please go to line C.' END IF 40 done: END RNH Enter your age: 25 Enter your sex: female Please go to line B.
A Use the IF construct when you want to execute a statement 1 or block of code only under specific conditions.
? The simplest form of the IF construct is a one-line statement:
$ IF cond_expr THEN statement
F cond_expr is a conditional expression. INTOUCH evaluates this : expression as either TRUE (1) or FALSE (0). G If the condition is TRUE, INTOUCH executes the statement following the ; THEN. If the condition is FALSE, INTOUCH skips the 8 statement following the THEN and goes to the next line.
F In the example program, when INTOUCH executes the first IF statement, J it evaluates the conditional expression, SEX$[1:1] = 'M'. IF the user is J 'Male' the condition is TRUE and INTOUCH executes the statement following the THEN and jumps to DONE:.
C IF can be used to execute a block of code. The IF block construct looks like this:
IF cond_expr THEN --- ! --- block of code --- END IF
J If the conditional expression is TRUE, INTOUCH executes the block of code < beginning on the next line. END IF marks the end of F this block of code. If the expression is FALSE, INTOUCH skips to the statement following the END IF.
? The ELSE option executes a statement if the conditional J expression is FALSE. The format of the IF statement with the ELSE option is:
3 IF cond_expr THEN statement ELSE statement
E When INTOUCH executes the IF statement, it evaluates the conditional I expression. If the expression is TRUE, the statement following the THEN J is executed. If the expression is FALSE, the ELSE statement is executed. $ (Please refer to previous example.)
RNH Enter your age: 19 Enter your sex: Female Please go to line A.
D In the above program, when INTOUCH executes the first IF statement, I it evaluates the expression, SEX$[1:1] = 'M'. Since the user is Female, G the expression is FALSE, so INTOUCH skips the THEN clause and jumps to H the ELSE clause. INTOUCH executes the code between the ELSE clause and the END IF.
J The ELSE option can be used to execute a block of code if the conditional M expression is FALSE. The IF construct with the ELSE option looks like this:
IF cond_expr THEN --- ! --- block of code ---
ELSE --- ! --- block of code --- END IF J If the conditional expression is TRUE, INTOUCH executes the block of code E between the IF and the ELSE statements. If the expression is FALSE, D INTOUCH executes the block of code between the ELSE and the END IF.
1 10 INPUT PROMPT 'Enter your age: ': age 2 INPUT PROMPT 'Enter your sex: ': sex$ < 20 IF UCASE$(sex$[1:1]) = 'M' THEN GOTO the_end PRINT " 30 IF age < 40 THEN + PRINT 'Please go to line A.' ELSE + PRINT 'Please go to line B.' END IF 40 the_end: END RNH Enter your age: 45 Enter your sex: female Please go to line B.
H In the above program, when INTOUCH executes the second IF statement, it N checks to see if "AGE < 40". Since AGE is not less than 40, the condition K is FALSE. INTOUCH skips the code following the THEN and jumps to the ELSE > clause. INTOUCH executes the code following the ELSE clause.
@ The ELSEIF option sets up a new condition to check. The 6 format of the IF construct with the ELSEIF option is:
IF cond_expr1 THEN --- ! --- block of code --- ELSEIF cond_expr2 THEN --- ! --- block of code ---
ELSE B --- ! --- block of code --- END IF K ELSEIF establishes a new condition. INTOUCH evaluates this condition. If K the condition is TRUE (1), INTOUCH executes the code following the ELSEIF. J If the condition is FALSE (0), INTOUCH jumps to the next clause in the IF construct.
1 10 INPUT PROMPT 'Enter your age: ': age 2 INPUT PROMPT 'Enter your sex: ': sex$ G 20 IF UCASE$(sex$[1:1]) = 'M' THEN GOTO the_end ELSE PRINT " 30 IF age < 20 THEN + PRINT 'Please go to line A.' 8 ELSEIF age > 19 AND age < 40 THEN + PRINT 'Please go to line B.' ELSE + PRINT 'Please go to line C.' END IF 40 the_end: END RNH Enter your age: 25 Enter your sex: Female Please go to line B.
G In the above program when INTOUCH executes the second IF statement, it J checks to see if "AGE < 20". Since AGE is not less than 20, the first J condition is FALSE. INTOUCH skips the code following the THEN and checks P the condition set up by the ELSEIF. Since "AGE > 19" and "AGE < 40", the E second condition is TRUE and INTOUCH executes the code following the F ELSEIF and prints 'Please go to line B.', then exits the conditional.
SELECT CASE main_expr CASE expr1[, expr2,...] --- --- block of code --- ! [CASE expr3[, expr4,...] --- --- block of code --- ...] = [CASE IS {numeric operator | boolean operator} expr5 --- --- block of code --- ...] [CASE ELSE --- --- block of code --- ...] END SELECT 10 DO 3 INPUT 'Your income per year': income 2 IF _BACK OR _EXIT THEN EXIT DO ! 20 SELECT CASE income CASE 0 # PRINT 'No income?' CASE IS < 0 = PRINT 'A negative income? You are in debt!' CASE IS > 0 + PRINT 'A positive income.' END SELECT LOOP 30 END RNH Your income per year? 0 No income? % Your income per year? -15000 , A negative income? You are in debt! $ Your income per year? 30000 A positive income. # Your income per year? exit
J Sometimes you need to compare one main expression with several values and @ execute a different block of code for each possible match. Use A SELECT CASE to check a set of conditions and execute code depending on the results.
B The SELECT CASE statement begins the construct and gives the main D expression (main_expr). In the example, the main expression = is INCOME. The CASE statements are compared with the B main expression. The first CASE expression (expr1) is 0. I Following this CASE is a block of code. If INCOME = 0 the block of code following CASE 0 is executed.
E 11.6.1 CASE expr, expr, expr...
; Each CASE statement can include several expressions I separated by commas. INTOUCH compares each of the expressions in a CASE B statement. If any of them match, the block of code following the CASE is executed.
10 DO 7 INPUT 'Procedure (add, del, exit)': pro$ ' IF _EXIT THEN EXIT DO " pro$ = UCASE$(pro$) 20 SELECT CASE pro$ CASE 'ADD' " PRINT 'Adding...' # CASE 'DEL', 'DELETE' $ PRINT 'Deleting...' END SELECT LOOP 30 END RNH ( Procedure (add, del, exit)? ADD Adding... ( Procedure (add, del, exit)? DEL Deleting... ) Procedure (add, del, exit)? EXIT
> The following example illustrates how to check for a range of values:
10 a = 5 SELECT CASE a # CASE 1 : PRINT 'one' * CASE 2 to 6 : PRINT 'range' ' CASE ELSE : PRINT 'else' END SELECT 20 b$ = 'c' SELECT CASE b$ # CASE 'a' : PRINT 'a' . CASE 'b' to 'e' : PRINT 'range' ' CASE ELSE : PRINT 'else' END SELECT 30 END RNH range range=
= The CASE ELSE option executes a block of code only if K none of the CASE expressions match. SELECT CASE with the CASE ELSE option looks like this:
SELECT CASE main expr [CASE expr1, expr2... --- --- block of code --- ...] < [CASE IS {numeric operator| boolean operator} expr3 --- --- block of code --- ...] CASE ELSE --- --- block of code --- END SELECT D CASE ELSE must follow the last CASE statement. If none of the CASE @ expressions match, INTOUCH executes the block of code following the CASE ELSE statement.
10 DO 8 INPUT 'Procedure (add, del, exit)' : pro$ ' IF _EXIT THEN EXIT DO # pro$ = UCASE$(pro$) 20 SELECT CASE pro$ CASE 'ADD' " PRINT 'Adding...' # CASE 'DEL', 'DELETE' $ PRINT 'Deleting...' CASE ELSE E MESSAGE ERROR: 'Procedure must be: add, del or exit' REPEAT DO END SELECT LOOP 30 END RNH ( Procedure (add, del, exit)? add Adding... ( Procedure (add, del, exit)? del Deleting... , Procedure (add, del, exit)? funny < Procedure must be add, del, or exit ) Procedure (add, del, exit)? EXIT;
< CASE IS lets you form a conditional expression to be K checked against the main expression. The format of the CASE IS option is:
+ CASE IS {relational operator} expr B When the CASE IS statement executes, INTOUCH compares expr 7 to the main_expr using the relational operator.
10 DO 3 INPUT 'Your income per year': income 2 IF _BACK OR _EXIT THEN EXIT DO ! 20 SELECT CASE income CASE 0 # PRINT 'No income?' CASE IS < 0 = PRINT 'A negative income? You are in debt!' CASE IS > 0 + PRINT 'A positive income.' END SELECT LOOP 30 END RNH % Your income per year? -15000 - A negative income? You are in debt! Your income per year? 0 No income? $ Your income per year? 25000 A positive income. # Your income per year? exit7
CHAIN 'file_spec'
8 10 LINE INPUT 'Your name (last, first)': name$ 7 OPEN #1: NAME 'storage.tmp', ACCESS OUTPUT PRINT #1: name$ CLOSE #1 : 20 INPUT 'Add to CLIENT structure (Y/N)': reply$ 0 IF reply$ = 'Y' THEN CHAIN 'ADD' 30 END RNH - Your name (last, first)? Woods, Jack ) Add to CLIENT structure (Y/N)? N
< CHAIN exits the current program and runs the program specified.
H file_spec is the specification for the program being chained to. K The file specification can be any string expression. INTOUCH searches for L the file specified. INTOUCH exits the current program and runs the program > named. Control does not return to the current program H when the chained program is finished. If INTOUCH cannot find the file, H or if the file is not an executable program, an exception is generated.
/ When INTOUCH executes the CHAIN statement, it:
N 11.8 Pass Commands to the Operating System
G 11.8.1 PASS [NOWAIT: | NORETURN:]
, PASS [NOWAIT: | NORETURN:] str_expr
7 10 INPUT 'What would you like to show': info$ ! 20 PASS 'SHOW ' + info$ 30 END RNH , What would you like to show? user t @ VAX/VMS User Processes at 9-MAY-1995 10:22:29.87 @ Total number of users = 1, number of processes = 1 < Username Node Interactive Subprocess Batch ' TESTER TTI 1
; Use PASS to perform system commands without leaving . the INTOUCH environment or exiting a program.
D PASS passes the specified string expression to the operating system C command interpreter. Generally, it passes the string to DCL. The G operating system will respond to the string as it would if you entered F it at the DCL $ prompt. When the system finishes, control returns to the INTOUCH program.
? When you use the NOWAIT option with PASS, the operating L system executes the passed command and immediately returns to INTOUCH 2 without waiting for the passed command to finish.
' 10 PASS NOWAIT: 'show user t' 20 END INTOUCH RNH INTOUCH @ VAX/VMS User Processes at 9-MAY-1995 10:23:19.87 @ Total number of users = 1, number of processes = 1 < Username Node Interactive Subprocess Batch ' TESTER TTI 1 end INTOUCH
; The PASS NORETURN statement passes a command to the 1 operating system but does not return to INTOUCH.
10 PRINT 'B E F O R E' 20 DELAY 2 ) 30 PASS NORETURN: 'show user t' 40 END RNH B E F O R E @ VAX/VMS User Processes at 9-MAY-1995 01:43:14.36 @ Total number of users = 1, number of processes = 1 < Username Node Interactive Subprocess Batch & TESTER TTI 1
$ 2 ? Branching means jumping from one part of a program to another. E Branching is especially useful when combined with conditionals. For E example, you can ask the user to choose a procedure. You can branch E to different subroutines in your program, depending on the procedure chosen.
? There are several statements used for branching: GOTO, GOSUB, E DISPATCH, ON GOTO, and ON GOSUB. GOTO causes INTOUCH to jump to the E specified location and continue normal program execution from there.
F GOSUB and DISPATCH execute routines and subroutines. Subroutines are J blocks of code that INTOUCH branches to, executes, and then returns from.
D GOTO, GOSUB, and DISPATCH cause unconditional branching. When they < are executed, INTOUCH jumps to the statement specified. To @ conditionally branch, combine these statements with conditional = statements. Two other constructs, ON GOTO and ON GOSUB, are E conditional. Both ON GOTO and ON GOSUB branch to one of a number of A places in the program depending an integer expression. When the A ON GOSUB construct is used, INTOUCH will return to the statement C following the ON GOSUB when the subroutine has finished executing.
F 11.9.1 Branching and Code Blocks
D Certain constructs (such as GOSUB) include a block of code which is F executed within the construct. You can transfer control within these 8 code blocks and out of these code blocks. For example:
, 10 DIM name$(4) . 20 FOR i = 1 TO 4 E INPUT 'Your name, please': name$(i) N branches within block -- IF name$(i) <> '' THEN GOTO hello = branches out of block -- IF _EXIT THEN EXIT FOR ( hello: 2 PRINT 'Hello!' & 30 NEXT i 0 40 PRINT 'Finished' * 50 END/
GOTO target
10 start: % INPUT 'Your Name': name$ * IF _EXIT THEN GOTO the_end # PRINT 'Hello, '; name$ GOTO start 20 the_end: END RNH Your Name? Tony Hello, Tony Your Name? Betty Hello, Betty Your Name? exit
< Use GOTO when you want to jump from one part of your program to another.
A target is the line to which control is being transferred. - target can be a label or line number.
Note
F It is recommended that you branch to labels rather than line numbers. C Should the line numbers change, the change would have no effect on your branching code.
I When INTOUCH executes a GOTO statement, it branches to the target F line specified. Any code between the GOTO and the target line L is skipped. INTOUCH continues normal program execution at the target line.
A ON int_expr GOTO target1 [, target2...] [ELSE statement]
? 10 ask: INPUT 'Procedure (1=add, 2=del, 3=exit)': pro ' 20 ON pro GOTO add, del, done add: PRINT 'Adding...' GOTO ask del: " PRINT 'Deleting...' GOTO ask 30 done: END RNH , Procedure (1=add, 2=del, 3=exit)? 2 Deleting... , Procedure (1=add, 2=del, 3=exit)? 1 Adding... , Procedure (1=add, 2=del, 3=exit)? 3
F Sometimes you want to jump to one of several places in your program. ; ON...GOTO lets you jump to one of several locations % depending on a condition you set up.
A int_expr is the integer expression or condition to check. B target1, target2 ... is a list of places to jump to. Each & target can be a label or line number.
F ON..GOTO branches to one of several targets depending on the value of = an integer expression. The simplest version of ON..GOTO is,
- ON int_expr GOTO target1, target2...
F int_expr is an integer expression whose value determines where G control is transferred. When INTOUCH executes the ON GOTO statement, J it evaluates the integer expression. If the value is 1, INTOUCH branches I to the first target in the list. If the value is 2, INTOUCH branches to the second target, and so on.
K If the expression does not evaluate to an integer, INTOUCH rounds it. The G value must be from 1 to the number of targets (unless there is an ELSE I clause). For example, if there are five targets, the integer value must be from 1 to 5.
G If the value is less than 1 or greater than the number of targets, and : there is no ELSE clause, INTOUCH generates an exception.
' Targets can be labels or line numbers.
I INTOUCH supports 128 targets for ON...GOTO. More targets than 128 gives ' an "expression too complex" exception.
; The ELSE option executes a statement if the integer G expression does not find a target. ON GOTO with the ELSE option looks like this:
? ON int_expr GOTO target1 [, target2...] ELSE statement
F ELSE must be followed by a statement. The ELSE is executed if H the integer value exceeds the number of targets in the list, is zero or is negative.
10 start: : INPUT 'Procedure (1=add, 2=del, 3=exit)': pro D 20 ON pro GOTO add, del, done ELSE PRINT 'Enter 1, 2 or 3' GOTO start add: PRINT 'Adding...' GOTO start del: " PRINT 'Deleting...' GOTO start 30 done: PRINT 'Finished' END RNH - Procedure (1=add, 2=del, 3=exit)? -2 Enter 1, 2 or 3 , Procedure (1=add, 2=del, 3=exit)? 1 Adding... , Procedure (1=add, 2=del, 3=exit)? 3 Finished7
GOSUB target . . . target --- --- block of code --- RETURN
10 GOSUB get_input # 20 PRINT 'Hello, '; name$ GOTO exit 30 get_input: + INPUT 'Enter your name': name$ " name$ = UCASE$(name$) RETURN 40 exit: PRINT 'Finished' 50 END RNH Enter your name? Julian Hello, JULIAN Finished
> Use GOSUB to jump to another location in your program, I execute the code at that location and then return to the place you left.
L GOSUB transfers control to a subroutine. The subroutine is a block of code. N INTOUCH executes the code, then returns to the statement following the GOSUB. A The target can be a label, a ROUTINE statement or a line number.
Note
F It is recommended that you branch to labels rather than line numbers. C Should the line numbers change, the change would have no effect on your branching code.
? If the target in the GOSUB statement does not exist, an G exception is generated. RETURN or END ROUTINE ends the subroutine and 8 transfers control to the statement following the GOSUB.
Note
C If your label or routine name contains an underscore (_) character B (e.g. ask_name, do_add), you do NOT need to use the word "GOSUB". > Under these conditions, the "GOSUB" is implied. For example: 9 using ASK_NAME would be the same as using GOSUB ASK_NAME
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