crystal-lang
Add missing StringScanner methods
Crystal's StringScanner does not support every method which Ruby's StringScanner does.
-
#beginning_of_line? -
#get_byte -
#getch -
#match -
#match? -
#matched? -
#matched_size -
#exist? -
#pos -
#rest? -
#rest_size -
#pre_match -
#post_match -
#<< -
#concat -
#unscan
I particularly need #getch to step through the string if #scan does not match the current position.
I don't know what you are doing, but << would be impossible to implement because strings are immutable.
I am porting this code to Crystal which walks a string attempt to match a series of regexes at each index, and if one of them matches wraps the matching string in ANSI styling: https://github.com/postmodern/hexdump.rb/blob/ead8dc6b45b281423ad7d4ea86d88f533ea0fbb4/lib/hexdump/theme/rule.rb#L129-L146
I even tried rewriting the code to only use String#match(regex,pos), but match(regex,pos) behaves differently from StringScanner#scan (will only match the regex at the current position, where as String#match will incrementally walk the string until it finds a match).
Yeah mutable methods like #<<, #concat, or even #string= are questionable, but I need #getch.
Have you tried Regex#match with Regex::Options::ANCHORED?
getch should be equivalent to scan(/./), though a Crystal implementation is certainly faster than that.
@HertzDevil ah clever and now the specs pass. Thank you!
I still think StringScanner should support more of Ruby's StringScanner to make porting to Crystal easier. getch, get_byte, match* methods seem like good candidates.
I agree, though I'll probably name them read_byte, read_char, etc., to match IO
@asterite Hi! I also need those methods when porting Ruby code to Crystal, so tried implementing #read_byte and #read_char methods.
Please take a look at #11785 .
With #16455, #getch could be replaced with .scan(1). #read_byte is omitted because it could lead to invalid character indices, but #current_byte is available to return the byte at the head.
