MM Comments - Answer Overflow

While glimpsing through the re2 source code I found this link in a comment https://swtch.com/~rsc/regexp/. It has some bare bones examples in C that may provide a less intimidating starting point than the re2 library for someone toying with the idea of implementing regexes for Mojo.

87 replies

MModular

•Created by Martin Dudek on 5/14/2024 in #questions

Regular Expression Engine for Mojo, any plans?

The only one I know of is a very simple (60 loc) regex match implementaion in Mojo by sstadic (https://github.com/sstadick/ExtraMojo/blob/main/ExtraMojo/regex/simple_re.mojo). However I'm also very interested to know of any plans. To my understanding Rust has a fast regex library.

87 replies

MModular

•Created by MM on 4/19/2024 in #questions

Accessing C struct members from external_call

For the record, here's how I tested the localeconv function of the C standard library. I only manage to print the decimal_point member all the other members are blank.

from sys.ffi import external_call

alias c_char = UInt8
alias LC_MONETARY = 4
var locale = "it_IT".data()._as_scalar_pointer()

# Return type struct lconv

@register_passable("trivial")
struct lconv:
   var decimal_point: Pointer[c_char]
   var thousands_sep: Pointer[c_char]
   var grouping: Pointer[c_char]    
   var int_curr_symbol: Pointer[c_char]
   var currency_symbol: Pointer[c_char]
   var mon_decimal_point: Pointer[c_char]
   var mon_thousands_sep: Pointer[c_char]
   var mon_grouping: Pointer[c_char]
   var positive_sign: Pointer[c_char]
   var negative_sign: Pointer[c_char]
   var int_frac_digits: c_char
   var frac_digits: c_char
   var p_cs_precedes: c_char
   var p_sep_by_space: c_char
   var n_cs_precedes: c_char
   var n_sep_by_space: c_char
   var p_sign_posn: c_char
   var n_sign_posn: c_char

var lc = external_call["localeconv", Pointer[lconv]]()
print(chr(lc[].decimal_point[0].to_int()))

from sys.ffi import external_call

alias c_char = UInt8
alias LC_MONETARY = 4
var locale = "it_IT".data()._as_scalar_pointer()

# Return type struct lconv

@register_passable("trivial")
struct lconv:
   var decimal_point: Pointer[c_char]
   var thousands_sep: Pointer[c_char]
   var grouping: Pointer[c_char]    
   var int_curr_symbol: Pointer[c_char]
   var currency_symbol: Pointer[c_char]
   var mon_decimal_point: Pointer[c_char]
   var mon_thousands_sep: Pointer[c_char]
   var mon_grouping: Pointer[c_char]
   var positive_sign: Pointer[c_char]
   var negative_sign: Pointer[c_char]
   var int_frac_digits: c_char
   var frac_digits: c_char
   var p_cs_precedes: c_char
   var p_sep_by_space: c_char
   var n_cs_precedes: c_char
   var n_sep_by_space: c_char
   var p_sign_posn: c_char
   var n_sign_posn: c_char

var lc = external_call["localeconv", Pointer[lconv]]()
print(chr(lc[].decimal_point[0].to_int()))

8 replies

MModular

•Created by MM on 4/19/2024 in #questions

Accessing C struct members from external_call

Thanks a lot! I have tried both DLHandle and external_call, but cannot get either one work. A good idea to check the source code of the ffi now that the std library is OS. I tried to read it through, but my grasp of mlir and C and low-level stuff is non-existant, so I'm afraid I was not able to find the answer to the question yet. I'm sure it must be possible though – it's hard to believe that the CPython integration could work with limited interoperability.

8 replies

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