diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/parcom.cr | 44 | ||||
| -rw-r--r-- | src/parcom/parser.cr | 4 |
2 files changed, 31 insertions, 17 deletions
diff --git a/src/parcom.cr b/src/parcom.cr index 0963184..60b8df0 100644 --- a/src/parcom.cr +++ b/src/parcom.cr @@ -12,9 +12,13 @@ module Parcom # The first and second arguments are types used for the parser's type. # The thirs argument is a string literal used for the name of the parser. # This is followed by any number of 2-tuples containing a variable name and - # an expression resolving to a `Parser(t.Class, _)`, whose success value will - # be stored in the aformentioned variable. The `finally` named argument is an - # expression that resolves to a `Parser(t.class, u.class)`. + # an expression resolving to a `Parser(t.class, _)`, whose success value will + # be stored in the aformentioned variable. The `make` named argument is an + # expression that resolves to a `Parser(t.class, u.class)`. This parser is + # the final step of the parser chain. The `pure` named argument is an + # expression that resolves to a `u.class`. This expression is passed to a + # call to `Parser(t.class, u.class).pure`, which will be the final step + # of the parser chain. # # Example: # ``` @@ -23,7 +27,7 @@ module Parcom # two_of_same_word = parser_chain Char, String, "two words", # {word, any_word}, # {_, ws}, - # finally: Parser.token_sequence(word.chars).map(&.join) + # make: Parser.token_sequence(word.chars).map(&.join) # # tokens = Tokens.from_string("foo foo") # result = two_of_same_word.parse(tokens) @@ -39,17 +43,27 @@ module Parcom # ``` # # This macro is based on Haskell's do-notation. - macro parser_chain(t, u, name, *steps, finally) - Parser({{t}}, {{u}}).new({{name}}) do |tokens| - {% for tup, index in steps %} - {{tup.last}}.and_then do |{{tup.first}}| - {% end %} - {{finally}} - {% for _, _ in steps %} - end - {% end %} - .parse(tokens) - end + macro parser_chain(t, u, name, *steps, make = nil, pure = nil ) + {% if make.nil? && pure.nil? %} + raise ArgumentError.new("Expected exactly one of 'make' and 'pure', but got neither") + {% elsif !make.nil? && !pure.nil? %} + raise ArgumentError.new("Expected exactly one of 'make' and 'pure', but got both") + {% else %} + Parser({{t}}, {{u}}).new({{name}}) do |tokens| + {% for tup, index in steps %} + {{tup.last}}.and_then do |{{tup.first}}| + {% end %} + {% if !make.nil? %} + {{make}} + {% else %} + Parser({{t}}, {{u}}).pure({{pure}}) + {% end %} + {% for _, _ in steps %} + end + {% end %} + .parse(tokens) + end + {% end %} end end diff --git a/src/parcom/parser.cr b/src/parcom/parser.cr index efa9780..398c95d 100644 --- a/src/parcom/parser.cr +++ b/src/parcom/parser.cr @@ -255,7 +255,7 @@ module Parcom parser_chain T, {U, V}, "#{@name} + #{other.name}", {x, self}, {y, other}, - finally: Parser(T, {U, V}).pure({x, y}) + make: Parser(T, {U, V}).pure({x, y}) end # Same as `#+`, but discards the second parser's result. @@ -440,7 +440,7 @@ module Parcom parser_chain T, Array(U), "<#{@name}> sep by <#{sep.name}>", {head, self}, {tail, (sep >> self).many}, - finally: Parser(T, Array(U)).pure(tail.unshift(head)) + make: Parser(T, Array(U)).pure(tail.unshift(head)) end end end |