Select Case

Basic implementation

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( temp <> 2 ) then goto cmplabel2
					scope
	print "2"				print "2"
					end scope
					goto endlabel

case else				cmplabel2:
					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

SELECT CASE

opens the implicit outer scope
declares the temp var

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 the end label

each CASE

if there was a previous CASE

closes the previous CASE's scope
emits a jump to the end label

emits the label for this CASE
emits a conditional branch that jumps to the next CASE if the CASE condition is not met
opens the CASE's scope
CASE ELSE does not 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 end label

any EXIT SELECTs jump immediately to the end label

SELECT CASE on strings/zstrings/fixstrs

dim s as string			dim s as string

				scope
select case s + "1"			dim temp as string

					fb_StrAssign( temp, s )
					fb_StrConcatAssign( temp, "1" )

case "1"				if( fb_StrCompare( temp, "1" ) <> 0 ) then goto cmplabel1
					scope
	print "1"				print "1"
					end scope
					goto endlabel

					cmplabel1:
end select				endlabel:
					fb_StrDelete( temp )    '' destroying the temp var at scope end
				end scope

				fb_StrDelete( s )

SELECT CASE on string/zstring/fixstr expressions uses a string temp var

probably because that's easiest
knowing the string length will potentially speed up the following comparisons
the dynamic memory allocation can be a slow down too

the string temp var is destroyed at scope end or scope breaks (e.g. reaching END SELECT, or EXIT FUNCTION from within a CASE block)

SELECT CASE on wstrings

dim w as wstring * 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_WstrDelete( temp )    '' destroying the temp var at scope end
					end scope

similar to SELECT CASE on zstrings, for wstring expressions a wstring is dynamically allocated
the temp wstring is treated much like 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 statement is just a simple variable access, then no temporary variable needs to be created. In this case, the given variable itself will be used in the comparisons at each case statement. For example:

dim i as integer		dim i as integer

				scope
select case i

case 1					if( i <> 1 ) then goto cmplabel1
					scope
	print "1"				print "1"
					end scope
					goto endlabel

end select				cmplabel1:
					endlabel:
				end scope

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Select Case