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Show 21 Th^ Conditional Sfatsni evL Syntax if <8tatecicnt> then <statement> else «.statements i statement ^henV-^ statemeriti ^else' statenent Semantics The value of the atateiaent tcilm^in^ the if muit be reducible to true or false (one ^r sero). if'a one« the statement-.following the theh' is eseecuted, then the statement following; the entire conditional statement is executed. If a zero, the sequence is similar to the above except the statement following the else is executed instead of the then. The entire conditional staterrient has a value equal to that of the executed branch. Note: This, the so-called "Long-form: of the if statement, is the only type presently available. It includes the "shortform: semantically since the empty statmnent is allowed. If it proves awkward to use, then the short form will also be added. Pragmatics ; There are only two jumps needed in the underlying environments Jump-Unconditional and Jump-if-top-stack-xero. These are invisible to the user and are ihserted during the parse. |
