Re: are there user defined infix operators?

[Uxio Prego]

Hey, thank you very much! I had lost all faith.

> You can write general rules say for prefix, infix, and postfix operators, 
> [...]

For simplicity I would be happy to consider only infix operators.

> [...] the actions put them onto to a stack with precedences and another for
> values. Then, when a new operator comes by, let the operators on the
> stack with higher precedences act on the value stack until something with
> a lower precedence appears, [...]

I read this twice and didn't understand anything. I read it once again and now
I understand you are proposing that when operators are used, I don’t really
use the syntax tree I'm generating with Bison _straightly_, but a more complex
syntax tree I'd be generating combining the natural tree that arises from the
grammar and other information in those data structures you propose. Did I
understand that right?

> On 8 Nov 2018, at 14:48, Hans Åberg <address@hidden> wrote:
> 
> 
>> On 2 Nov 2018, at 17:53, Uxio Prego <address@hidden> wrote:
>> 
>> More specifically, I'm curious to know if Bison can modify precedences
>> at parsing time according user sentences, now referring as user not the
>> programmer who wrote the *.y doc but the programmer writing a program
>> parsed by the parser generated from the *.y doc.
> 
> You can't but:
> 
> You can write general rules say for prefix, infix, and postfix operators, and 
> then the actions put them onto to a stack with precedences and another for 
> values. Then, when a new operator comes by, let the operators on the stack 
> with higher precedences act on the value stack until something with a lower 
> precedence appears, and put the new operator onto the stack. Continue until 
> the end symbol comes by that has the lowest precedence. Operator 
> associativity is handled by viewing left and right hand side precedences as 
> different.
> 
>