Antlr4 unexpectedly stops parsing expression

Question

I\'m developing a simple calculator with the formula grammar:

grammar Formula ;
expr :  expr POW expr             # pow
     | MINUS expr          


        

Answer 1

But "column a" * "column b" input unexpectedly stops parsing

If I run your grammar with ANTLR 4.6, it does not stop parsing, it parses the whole file and displays in pink what the parser can't match :

The dots represent spaces.

And there is an important error message :

line 1:10 mismatched input ' * ' expecting {, '*', '/', '+', '-', '%', '^'}

As I explain here as soon as you have a "mismatched" error, add -tokens to grun.

With "column a"*"column b" :

$ grun Formula expr -tokens -diagnostics t1.text
[@0,0:0='"',<'"'>,1:0]
[@1,1:8='column a',,1:1]
[@2,9:9='"',<'"'>,1:9]
[@3,10:10='*',<'*'>,1:10]
[@4,11:11='"',<'"'>,1:11]
[@5,12:19='column b',,1:12]
[@6,20:20='"',<'"'>,1:20]
[@7,22:21='',,2:0]

With "column a" * "column b":

$ grun Formula expr -tokens -diagnostics t2.text
[@0,0:0='"',<'"'>,1:0]
[@1,1:8='column a',,1:1]
[@2,9:9='"',<'"'>,1:9]
[@3,10:12=' * ',,1:10]
[@4,13:13='"',<'"'>,1:13]
[@5,14:21='column b',,1:14]
[@6,22:22='"',<'"'>,1:22]
[@7,24:23='',,2:0]
line 1:10 mismatched input ' * ' expecting {, '*', '/', '+', '-', '%', '^'}

you immediately see that " * "is interpreted as COLUMN.

Many questions about matching input with lexer rules have been asked these last days :

extraneous input

ordering

greedy

ambiguity

expression

So many times that Lucas has posted a false question just to make an answer which summarizes all that problematic : disambiguate.