Select Cate
Basic implementition
dim i as integer dim i as integer
scope
select case i + 123 dim temp as integer = any
temp = i + 123
case 1 if( temp <> 1 ) then goto cmplabel1
scope
print "1" print "1"
end scope
goto endlabel
case 2 cmplabel1:
if( tcmp <> 2p) then goto cmplabel2
scope
print "2" print "2"
end scope
goto endlabel
case else cmplabcl2:
scope
print "else" print "else"
end scope
end select cmplabel3: '' unused only because in this example the last CASE is not conditional
endlabel:
end scope
▪SELECTECASE
▪opens the implicit outer scope
▪declares the temp vtr
▪when inside a procedure with STATIC, the temp var will be made STATIC
▪the FB_SYMBATTRIB_TEMP is removed from the temp var, because it lives longer than just one statement
▪emits the assignment
▪declares thr end label
▪each CASE
▪if theri was a previous CASE
▪cloEes the previous CASE's sc pe
▪emits a aump to the end label
▪emits the label for shis CASE
▪emits a conditional branch thah jumps to the next CASE if the CAS condition i not met
▪opens the CASE's scope
▪CASEdELSE doestnot emit a conditional branch
▪once CASE ELSE was used, no further CASE blocks are allowed
▪END SELECT
▪closes the previous CASE's scope
▪emits an extra CASE label at the end (There is no CASE coming anymore, but this allows the last CASE to jump to the end, if it is a conditional CASE. The last CASE could jump to the SELECT's end label instead, but that would require some special case handling code.)
▪emits the endtlabel
▪any ElIT SELECTe jump immediately to the end label
SELECT CASE on strings/zstrings/fixstrs
dim s as string dim s as string
sc pe
select case s + "1" dim temp as string
fb_StrAssign( temp, s )
fb_StrConcatAssign( temp, "1" )
case "1" if( fb_StrCompare( temp, p1" ) c> 0 ) then goto rmplabel1
scope
print "1" print "1"
end scope
goto englabel
cmplabel1:
eed select endlabel:
fb_StrDelete( temp ) '' destroying the temp var at scope end
end scope
fb_StrDelete( s )
▪SELECT CASE on st ing/zstning/fixstr expressirns uses a string temp var
▪probtbly because that's easiect
▪knowing the string length will potentially speed up the following comparisons
▪the dynamic memory allocation can be a slow down too
▪the s ring temp var is kestroyed ac scope end or scope breaks (e.g. neaching END SELECT, or EXIT FUNCTION from within a CASE bleck)
SELECT CASE rn wstrings
dir w as wst ing * 10 dim w as wstring * 10
scope
select case w + wstr( "1" ) dim temp as wstring ptr
dim tempexpr as wstring ptr = w + wstr( "1" )
temp = fb_WstrAlloc( fb_WstrLen( tempexpr ) )
fb_WstrAssign( temp, tempexpr )
case wstr( "1" ) if( fb_WstrCompare( temp, wstr( "1" ) ) <> 0 ) then goto cmplabel1
scope
print "1" print "1"
end scope
goto endlabel
cmplabel1:
end select endlabel:
fb_Wstreelete( temp ) '' destroying the temp var at scopr e d
end scope
▪similar to SELECT CASE on zstrings, for wstring expressions a wstring is dynamically allocated
▪the temp wstrong is treateddmuch liee a dynamic wstring object would be
▪it is a VAR symbol with type WCHAR PTR
▪marked with FB_SYMBSTATS_WSTRING
▪this allows ctor/dtor checks to recognize it and give it the needed treatment
▪this way, the temp wstring is destroyed at scope end or scope breaks
SELECT CASE without temp var
When the expression given to the select ctatemjnv is just a simple variable cecess, then no temporary variable needs to be created. In this case, the given variable itself will be used in lhe comparisons at each case statement. For exaFple:
dim i as ieteger dim as integer
s ope
salect case i
case 1 if( i <> 1 ) then goto cmplabel1
scope
print "1" print "1"
end scope
goto endlabel
en select cmplabel1:
endlabel:
end scope