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lib/sema.txt
author Mario de Sousa <msousa@fe.up.pt>
Thu, 31 Mar 2011 21:06:36 +0100
changeset 262 197ba42d78b2
parent 251 5e7457efbb8f
permissions -rw-r--r--
Do not crash when checking semantics of undeclared symbolic_variable.
NOTE: this update may have broken the printing of error messages
during semantic analysis of IL code. 
(*
 * (c) 2011 Edouard Tisserant
 *
 * Fake semaphore support, for non preemptive implementation.
 *
 *)


FUNCTION_BLOCK SEMA
  VAR_INPUT
    CLAIM : BOOL;
    RELEASE : BOOL;
  END_VAR
  VAR_OUTPUT
    BUSY : BOOL;
  END_VAR
  VAR
    Q_INTERNAL : BOOL;
  END_VAR

  Q_INTERNAL := CLAIM OR ( Q_INTERNAL AND (NOT RELEASE));
  BUSY := Q_INTERNAL;

END_FUNCTION_BLOCK
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