diff options
Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 39 |
1 files changed, 12 insertions, 27 deletions
@@ -40,14 +40,14 @@ expr | func_call | int | id - | '(' expr ')' #ast expr + | l_paren expr r_paren #ast expr ; func_call - : id '(' args ')' #ast id args - | id '(' ')' #ast id + : id l_paren args r_paren #ast id args + | id l_paren r_paren #ast id ; args - : args ',' expr #ast args... expr + : args comma expr #ast args... expr | expr ; @@ -65,6 +65,12 @@ mul : '*'; div : '/'; +l_paren + : '('; +r_paren + : ')'; +comma + : ','; ``` Save the above grammar to a file in UTF-8. In this explanation, the file name is `expr.vartan`. @@ -216,11 +222,7 @@ func printSyntaxError(w io.Writer, synErr *SyntaxError, gram Grammar) { msg = fmt.Sprintf("'%v' (<invalid>)", string(tok.Lexeme())) default: if term := gram.Terminal(tok.TerminalID()); term != "" { - if alias := gram.TerminalAlias(tok.TerminalID()); alias != "" { - msg = fmt.Sprintf("'%v' (%v)", string(tok.Lexeme()), alias) - } else { - msg = fmt.Sprintf("'%v' (%v)", string(tok.Lexeme()), term) - } + msg = fmt.Sprintf("'%v' (%v)", string(tok.Lexeme()), term) } else { msg = fmt.Sprintf("'%v'", string(tok.Lexeme())) } @@ -263,7 +265,7 @@ expr ```sh $ echo -n 'foo+99?' | go run . -1:7: unexpected token: '?' (<invalid>): expected: <eof>, +, -, *, / +1:7: unexpected token: '?' (<invalid>): expected: <eof>, add, sub, mul, div exit status 1 ``` @@ -435,23 +437,6 @@ See [Error recovery](#error-recovery) section for more details on the `#recover` ### Directives for terminal symbols -#### `#alias <alias: String>` - -An `#alias` directive aliases for a terminal symbol. You can use the alias in error messages, for example. - -example: - -``` -#name example; - -s - : id - ; - -id #alias 'identifier' - : "[A-Za-z_][0-9A-Za-z_]*"; -``` - #### `#mode {<mode-name: Identifier>}`, `#push <mode-name: Identifier>`, and `#pop` A terminal symbol with a `#mode` directive is recognized only on a specified mode (`mode-name`). The mode is lexer state, which a `#push` directive and a `#pop` directive can switch. |