CODEWITHSUNDEEP
objective-cparsekit
Mike Trelinski
Mike Trelinski

Reputation: 25

Writing a ParseKit grammar with a varying number of fields (in order)

I'm not super experienced in writing grammars, but let's say I have a record type like these: (examples)

record # 1 source ages params A = 1 and b = 2 fields are A, B, C with values 1, 2, 3;
record # 2;
record # 3 source ages;
record # 4 params A = 1 and b = 2 fields are A, B, C with values 1, 2, 3;
record # 5 source ages fields are A, B, C with values 1, 2, 3;
record # 6 with values 1, 2, 3;

Basically:

  1. Must start with "record # Number" and end with a semi-colon.
  2. May contain 0 or 1 captures in the following order:
  3. source dataset
  4. parameters of dataset
  5. fields from dataset
  6. values from dataset

Here is my grammar, it's not working:

--- start grammar:

@start = record;

record = 'record' '#' numeric rest* ';';
rest = 'source' alphanumeric paramsAndOrFieldsAndOrWithValues*;
paramsAndOrFieldsAndOrWithValues = (paramsList)? (fieldsList)? (valuesList)?;
paramsList = 'params' alpha expr numeric ('and' alpha expr numeric)*;
fieldsList = 'fields' 'are' alpha (comma alpha)*;
valuesList = 'with' 'values' numeric (comma numeric)*;


alpha = Word;
numeric = Number;
alphanumeric = (alpha | numeric | '_' | '.');
comma = ',';
expr = '=';

--- end grammar

@"Developer from ParseKit", can you please help me?

Thanks :)

Upvotes: 2

Views: 273

Answers (1)

Todd Ditchendorf
Todd Ditchendorf

Reputation: 11337

Developer of ParseKit here.

Your grammar is a little bit off. I worked up a grammar which matches your example input. I've run this using the DebugApp target, and can confirm that it works for your example.

@start = records;
records = record+;
record = prefix source? params? fields? values? suffix;

prefix = 'record' '#' Number;
suffix = ';';

// source
source = 'source' Word;

// params
params = 'params' expr ('and' expr)*;
expr = name '=' Number;
name = Word;

// fields
fields = 'fields' 'are' name (',' name)*;

// values
values = 'with' 'values' val (',' val)*;

val = Number;

Upvotes: 1

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