[Newbies] Efficient date parsing

[Ramon Leon]

cient date parsing
> 
> 
> I have a large file with dates in the format '2001-11-04'. As 
> I couldn't find a method to change to date, I'm doing:
>       date := self dateFrom: (dateString  subStrings: '-').
> 
> dateFrom: anArray
> 	"anArray should be like #('2005' '09' '06')"
> 	^Date year: anArray first asInteger month: anArray 
> second asInteger day:
> anArray third asInteger
> 
> This works, but profiling shows half the work in loading the 
> file is in
> dateFrom:
> 
> Is there a more efficient way? Is there a standard method I've missed?

On my Date class, class side, I use the following extention methods for
parsing dates.

fromString: aString format: aFormat 
	aFormat = #dmy
		ifTrue: [^ self readEuro: aString readStream ].
	aFormat = #iso8601
		ifTrue: [^ self readISO: aString readStream].
	^ self fromString: aString

readEuro: aStream 
	"Read a Date in euro format dd-mm-yyyy"
	| day month year |
	aStream skipSeparators.
	day := Integer readFrom: aStream.
	[aStream peek isDigit]
		whileFalse: [aStream skip: 1].
	month := Integer readFrom: aStream.
	[aStream peek isDigit]
		whileFalse: [aStream skip: 1].
	year := Integer readFrom: aStream.
	^ self
		newDay: day
		month: month
		year: year

readISO: aStream 
	"Read a Date in ISO-8601 format yyyy-mm-dd"
	| day month year |
	aStream skipSeparators.
	year := Integer readFrom: aStream.
	[aStream peek isDigit]
		whileFalse: [aStream skip: 1].
	month := Integer readFrom: aStream.
	[aStream peek isDigit]
		whileFalse: [aStream skip: 1].
	day := Integer readFrom: aStream.
	^ self
		newDay: day
		month: month
		year: year

Ramon Leon
http://onsmalltalk.com