6 Branching and Subroutines
IF numeric expression THEN line id
NOTE: Working with line number is not recommened and doesn't work in the IDE.
If the numeric expression has a value other than 0, it is considered true and branching occurs to the specified line id. If its value is 0 (false), execution continues with the line following the IF THEN statement. For example:
10 INPUT A 20 IF A THEN 50 30 PRINT "A=0" 40 GOTO 10 50 PRINT "A=";A 60 ENDThe IF THEN statement is used most often with relational operators. For example:
100 INPUT "HOURS WORKED?";Hours 110 IF Hours>40 THEN Overtime 120 DISP "NO OVERTIME ENTERED." 130 GOTO 100 140 Overtime: Over=Hours-40 150 PRINT "OVERTIME PAY =";Over*Pay*1.5 160 GOTO 100Another form of the IF THEN statement provides conditional execution of a statement without branching. Syntax is as follows:
IF numeric expression THEN statement
When the value of the numeric expression is not 0 (true), the statement is executed. When the value of the numeric expression is 0 (false), execution continues with the following line. For example:
200 READ X,Y 210 IF X=Y THEN PRINT "X=Y" 220 PRINT "X=";X,"Y=";YA special expression exists for User Defined Types.
IF Instance_name IS A Type_name THEN
With this expression it is possible to find out if the given Instance has has been derived from the given Type. If the given Instance and the given Type have been derived from the same Base_type, then the expression is true, too.
IF My_car IS A Car THEN CALL Write_car(STRUCT My_car)
All executable Eloquence statements are allowed following THEN.
The following statements are not allowed after THEN since they are declaratory statements, not executable statements:
COM INTEGER DATA OPTION BASE DIM REAL DEF FN REM FN END SHORT END SUB IMAGE SUBENDHere is another example use of IF THEN, which branches to one of many routines depending on the input response.
10 INPUT "DO YOU WISH DAILY, WEEKLY, OR MONTHLY REPORTS?";Report$ 20 IF UPC$(Report$[1,1])="D" THEN Daily 30 IF UPC$(Report$[1,1])="W" THEN Weekly 40 IF UPC$(Report$[1,1])="M" THEN Monthly 50 DISP "INCORRECT ENTRY" 60 WAIT 2000 70 GOTO 10 80 Daily: ! Print daily report. . . . 130 STOP 140 Weekly: ! Print weekly report. . . . 220 STOP 230 Monthly: ! Print monthly report. . . . 300 Continue: ! Continue program. . .