Basic HTML version of Foils prepared March 30 97

Foil 26 Control Structures -- while,until (Chapter 4 of the Llama Book)

From PERL4 Tutorial for CPS616 Computational Science for Information Age Course CPS616 -- February 1995. by Geoffrey C. Fox
The simplest iterations are while and until
while ( TESTEXPRESSION) {
  • some statement block; # Execute if TESTEXPRESSION true
  • }
is illustrated by
while ( <STDIN> ) {
  • Process Current Input line; # until end-of-file seen by null character in <STDIN>
  • }
Conversly we can wait for a signal to stop something
until ( TESTEXPRESSION) {
  • some statement block; Execute if TESTEXPRESSION false
  • }

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