PowerD.html - Conditional statement (IF)

Syntax:
IF-statement syntax can be quite variable. Here follows single and multiple line syntaxes.

  IF <exp> THEN <statement> [ ELSE <statement> ]

  IF <exp>
    <statements>
  [ ELSEIF <exp>
    <statements> ]    // multiple ELSEIFs may occur
  [ ELSE
    <statements> ]
  ENDIF

  IF <exp>       <statement>
  [ ELSEIF <exp> <statement> ]    // multiple ELSEIFs may occur
  ELSE           <statement>

Multiple-line syntaxes (last two above) can be combined. Single statement can be replaced be DO keyword. If you use DO keyword after ELSE keyword, you mustn't use ENDIF keyword:

  IF <exp>     [ DO <statements> ]
  ELSEIF <exp> [ DO <statements> ]
  ELSE           DO <statements>

When using multiple line syntax, you can use also single-line ELSE definition, which shorts down source length. This definition leaves ENDIF keyword:

  IF <exp>
    <statements>
  [ ELSEIF <exp>
    <statements> ]    // multiple ELSEIFs may occur
  ELSE <statement>

Negated condition:
If You add 'N' after IF or ELSEIF, the result of contition will be negated:
```
  IF a>b
  IF a=NIL
```
is the same as:
```
  IFN a<=b
  IFN a
```

Returning values:

  a:=IF <exp> THEN <texp> ELSE <fexp>

  a:=IF <exp>
       <statements>
       EXIT <texp>
     [ ELSEIF <exp>
       <statements>
       EXIT <eexp> ]    // multiple ELSEIFs may occur
     ELSE
       <statements>
       EXIT <fexp>
     ENDIF

  a:=IF <exp>       <texp>
     [ ELSEIF <exp> <eexp> ]    // multiple ELSEIFs may occur
     ELSE           <fexp>

IF <exp> is TRUE, a will contain <texp> else a will contain <fexp>. If ELSEIF <exp> is TRUE, a will contain <eexp>. You can also return multiple values. See EXIT keyword for more information.

Examples:

  IF age<10 PrintF('Too young!\n')
  ELSEIF age<70
    PrintF('Well, your age is acceptable.\n')
    ok:=TRUE
  ELSE DO PrintF('Too old!\n'); ok:=FALSE