Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
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notallowedonconstantcopies.Avariableholdingaconstantcopyisautomaticallymadeuninitializedwhencontrolleavesthescopeofthevariable.<br />
Thefollowingisanexampleoftheinspectstatement. inspectcharinstring begin where(char='X'<strong>and</strong>positionofchar>2) 11.<strong>Hermes</strong>Operations113<br />
tweentheinspectstatement<strong>and</strong>thesimilarstatementusingtheoperation the-element. mentasthevariableholdingtheconstantcopy.Notethedierencesbe-<br />
sionastheelementvariableofaselector,<strong>and</strong>(2)withintheinsertstate-<br />
c:=charinstringwhere(char='X'<strong>and</strong>positionofchar>2); endinspect; Notethedoubleuseofthevariablechar|(1)withinthewhereexpres-<br />
insertcopyofcharintostring2;<br />
copy.Itisillegaltoapplyinsertdirectlytocharbecauseitisconstant, operationcanbeappliedtoconstantcopiesbutnottoordinarycopies. butitislegaltoapplyinsertdirectlytoc.Theposition-of-element mentproducesaconstantcopy,whereasthe-elementproducesanordinary whereasthe-elementworksonlywithcopyabletypes.Theinspectstate-<br />
havebeenpreviouslydeclared.Theinspectstatementworksforalltypes, Thetypestateonentrytothemainclauseoftheinspectstatement Theinspectstatementintroducesadeclarationofchar,whereascmust insertcintostring2;<br />
normally. For-Inspect mainclause,exceptthattheinspectvariablebecomesuninitialized.Ifthe mainclausecannotexitnormally,thentheinspectstatementcannotexit fromtheinspectstatementisthesameasthetypestateonexitfromthe theinspectvariableisintheelementtypestate.Thetypestateonexit isthesameasthetypestatepriortotheinspectstatementexceptthat<br />
lectedsubsetofthetable.Thetablemustbeinitialized.Themainclause (theclausefollowinginspect)isexecutedonceforeachselectedelement. Avariablewiththesamenameastheelementvariableoftheselectorholds Thefor-inspectstatementiteratesovertheelementsofatableorase-<br />
compound{statement<br />
tothefor-inspectstatementisusedtodeterminetheselectedvalues; aconstantcopyoftheselectedelement.Thevalueofthetableonentry ::=forselectorinspect<br />
anychangestothetablemadefromwithintheiteratedclausewillnotaffectwhichvaluesareselected.Ifthetableisordered,theelementswillbe<br />
endfor [statement;]...
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