On 23.01.19 13:30, nop head wrote: > Isn't the let thing a syntax error? I.e. the arguments to let should > be assignment statements with name = expression, not just an > expression. let(a 42), let(a =)  and let(=42) are all syntax errors as > expected. > You can see it that way. Either we catch that during parsing or during runtime. Catching it in the parser requires more work, then catching it during runtime. Hm - I think you right, I'll give modifying the parser a try. With kind regards, Michael Frey

Yes it looks like a parser bug to me because there is no equals sign. I don't know how it gets an empty variable name and carries on. If you actually give it an equals sign without a variable name it does give a syntax error. The grammer here http://files.openscad.org/grammar.xhtml says it should be ID = expr. How does the parser not give an error for just expr? -- Sent from: http://forum.openscad.org/

On 23.01.19 19:16, nophead wrote: > Yes it looks like a parser bug to me because there is no equals sign. I don't > know how it gets an empty variable name and carries on. If you actually give > it an equals sign without a variable name it does give a syntax error. > > The grammer here http://files.openscad.org/grammar.xhtml says it should be > ID = expr. How does the parser not give an error for just expr? > Modules and Functions accept named and unnamed variables. TOK_LET beeing a valid module identifier: https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L341-L345 https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L351-L351 That is why I can not easily change the parser. Any way: Let has has two more forms: Expression: https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L490 and list_comprehension_element: https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L521 Eitherway, let takes arguments_call: https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L628 which consists of many argument_call https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L647 and there is cause: https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L648-L651 Note that we need this for unnamed parameters for functions and modules calls. To resolve the issue with let, we would need to duplicate/modify those data structures. I do not like the idea of increasing the parser complexity by duplicating part of it. I know that it is kind of hard to follow this links and my description, but that is the nature of GNU/Bison parsers. It takes time getting used to reading them. With kind regards, Michael Frey

"Let" is not the only strange case. The following expressions are syntactically acceptable too: for( 0!=1 ); for( i=[0:10], i!=2); but do not expect any reasonable semantics they might induce. Em qua, 23 de jan de 2019 às 18:17, nophead <nop.head@gmail.com> escreveu: > Yes it looks like a parser bug to me because there is no equals sign. I > don't > know how it gets an empty variable name and carries on. If you actually > give > it an equals sign without a variable name it does give a syntax error. > > The grammer here http://files.openscad.org/grammar.xhtml says it should be > ID = expr. How does the parser not give an error for just expr? >

So the grammar documentation I found has nothing to do with the parser? That grammar says let takes statements not arguments_call. That is the bug. On Wed, 23 Jan 2019 at 20:41, Michael Frey <michael.frey@gmx.ch> wrote: > On 23.01.19 19:16, nophead wrote: > > Yes it looks like a parser bug to me because there is no equals sign. I > don't > > know how it gets an empty variable name and carries on. If you actually > give > > it an equals sign without a variable name it does give a syntax error. > > > > The grammer here http://files.openscad.org/grammar.xhtml says it should > be > > ID = expr. How does the parser not give an error for just expr? > > > > Modules and Functions accept named and unnamed variables. > > TOK_LET beeing a valid module identifier: > > > https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L341-L345 > > > https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L351-L351 > > That is why I can not easily change the parser. > > Any way: Let has has two more forms: > > Expression: > > > https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L490 > > and list_comprehension_element: > > > https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L521 > > Eitherway, let takes arguments_call: > > > https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L628 > > which consists of many argument_call > > > https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L647 > > and there is cause: > > > https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L648-L651 > > Note that we need this for unnamed parameters for functions and modules > calls. > > To resolve the issue with let, we would need to duplicate/modify those > data structures. > > I do not like the idea of increasing the parser complexity by > duplicating part of it. > > > I know that it is kind of hard to follow this links and my description, > but that is the nature of GNU/Bison parsers. > > It takes time getting used to reading them. > > > With kind regards, > > Michael Frey > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

Sorry, I meant assignments, not arguments_call. On Wed, 23 Jan 2019 at 20:50, nop head <nop.head@gmail.com> wrote: > So the grammar documentation I found has nothing to do with the parser? > That grammar says let takes statements not arguments_call. That is the bug. > > On Wed, 23 Jan 2019 at 20:41, Michael Frey <michael.frey@gmx.ch> wrote: > >> On 23.01.19 19:16, nophead wrote: >> > Yes it looks like a parser bug to me because there is no equals sign. I >> don't >> > know how it gets an empty variable name and carries on. If you actually >> give >> > it an equals sign without a variable name it does give a syntax error. >> > >> > The grammer here http://files.openscad.org/grammar.xhtml says it >> should be >> > ID = expr. How does the parser not give an error for just expr? >> > >> >> Modules and Functions accept named and unnamed variables. >> >> TOK_LET beeing a valid module identifier: >> >> >> https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L341-L345 >> >> >> https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L351-L351 >> >> That is why I can not easily change the parser. >> >> Any way: Let has has two more forms: >> >> Expression: >> >> >> https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L490 >> >> and list_comprehension_element: >> >> >> https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L521 >> >> Eitherway, let takes arguments_call: >> >> >> https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L628 >> >> which consists of many argument_call >> >> >> https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L647 >> >> and there is cause: >> >> >> https://github.com/openscad/openscad/blob/9f861b119fa61c0027e657c452ce02549affc500/src/parser.y#L648-L651 >> >> Note that we need this for unnamed parameters for functions and modules >> calls. >> >> To resolve the issue with let, we would need to duplicate/modify those >> data structures. >> >> I do not like the idea of increasing the parser complexity by >> duplicating part of it. >> >> >> I know that it is kind of hard to follow this links and my description, >> but that is the nature of GNU/Bison parsers. >> >> It takes time getting used to reading them. >> >> >> With kind regards, >> >> Michael Frey >> >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >

> On Jan 23, 2019, at 15:50, nop head <nop.head@gmail.com> wrote: > > So the grammar documentation I found has nothing to do with the parser? That grammar says let takes statements not arguments_call. That is the bug. > I cannot remember how I generated that diagram. It probably was an experiment where I tried to describe the grammar using EBNF or smth., but didn't fully encode the OpenSCAD grammar.. -Marius

Is it easy to change the parser to match the grammar? I can't see why let should use the arguments_call rule. On Sat, 26 Jan 2019 at 18:02, Marius Kintel <marius@kintel.net> wrote: > > On Jan 23, 2019, at 15:50, nop head <nop.head@gmail.com> wrote: > > > > So the grammar documentation I found has nothing to do with the parser? > That grammar says let takes statements not arguments_call. That is the bug. > > > I cannot remember how I generated that diagram. It probably was an > experiment where I tried to describe the grammar using EBNF or smth., but > didn't fully encode the OpenSCAD grammar.. > > -Marius > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

> On Jan 26, 2019, at 13:07, nop head <nop.head@gmail.com> wrote: > > Is it easy to change the parser to match the grammar? I can't see why let should use the arguments_call rule. > The let() function yes, but the let() module isn't part of the grammar it's just a built-in module. -Marius

Oh I see, that is why it has grammar of a module call, which is similar to assignments but not quite correct. On Sat, 26 Jan 2019 at 18:13, Marius Kintel <marius@kintel.net> wrote: > > On Jan 26, 2019, at 13:07, nop head <nop.head@gmail.com> wrote: > > > > Is it easy to change the parser to match the grammar? I can't see why > let should use the arguments_call rule. > > > The let() function yes, but the let() module isn't part of the grammar > it's just a built-in module. > > -Marius > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >