How can I write a (La)TeX command that replaces all [ with { and all ] with }, assuming that every [ has a matching ], and that any braces between the [ and ] are balanced? It needs to be able to deal with nested brackets.
For example, I want to be able to write a command \mynewcommand so that \mynewcommand{{[[{1}{2}][{3}{4}]]}} is the same as \mycommand{{{{{1}{2}}{{3}{4}}}}}.
Probably the easiest way is to use e-TeX and \scantokens
\newcommand*\mycommand[1]{%
\begingroup
\everyeof{\noexpand}%
\endlinechar=-1\relax
\catcode`\[=1\relax
\catcode`\]=2\relax
\edef\temp{\scantokens{#1}}%
\expandafter\endgroup
\expandafter\def\expandafter\temp\expandafter{\temp}%
}
This will define \temp with the material in #1 but with every "[" ... "]" pair turned into a TeX brace group ("{" ... "}"). You can then use \temp to do whatever you want. As I say, this requires e-TeX, which is available in all modern TeX systems.
Related
I need help with preg_match in lua, I have tried some different ways.
I tried with string.match and string.find, but I can't write the pattern correctly.
I know this way in php, but need similar way in lua
$s = "/testas [51]";
preg_match("#/testas [(.*)]#", $s, $out);
print_r($out);
I want to get an integer in [ ].
To get the integer inside [ ], try this code:
print(string.match(s,"/testas%s+%[(%d+)%]"))
The pattern comes directly from the specification of the task. We just need to escape the brackets.
I'm trying to do this example :
sentence="{My name is {Adam} and I don't work here}"
Result should be 'Adam'
So what I'm trying to say is however many parenthesis exist I want the result to show the value of the last closed parenthesis
It's not clear from your question, but if there can only ever be one set of outer braces at any level (i.e. "{My name} {is {Adam}}" and "{My {name} is {Adam}}" are invalid input), you can take advantage of the fact that what you want is the last opening brace in the sentence.
def deepest(sentence):
intermediate = sentence.rpartition("{")[-1]
return intermediate[:intermediate.index("}")]
deepest("{My name is {Adam} and I don't work here}")
# 'Adam'
deepest("{Someone {set us {{up} the bomb}!}}")
# 'up'
The regex answer also makes this assumption, though regex is likely to be much slower. If multiple outer braces are possible, please make your question clearer.
You can't just index strings like that... The best way is to use a clever regex:
>>> import re
>>> re.search(r'{[^{}]*}', "{My name is {Adam} and I don't work here}").group()
'{Adam}'
This regex pattern essentially searches for every set of {} that doesn't have the characters { or } in them.
I'm trying to see if I can use Red (or Rebol) to implement a simple DSL. I want to compile my DSL to source code for another language, perhaps Red or C# or both - rather than directly interpreting and executing it.
The DSL has only a couple of simple statements, plus an if/else statement.
Statements can be grouped into rules. A rule would get translated into a function definition, with each statement the equivalent statement in the target language.
The parse capability in Red/Rebol is great and lets me implement a parser very easily - in effect it's basically just the definition of the grammar itself.
However I haven't been able to find any examples of how to take the next steps, specifically handling an if statement and translating it to other source code.
Translating an if statement seems a good example of something minimal but still slightly tricky - because in Red having an else means you need to change the if to an either, rather than just an extra optional else.
Traditionally, during parsing I would build an abstract syntax tree, and then have functions to operate on the AST and generate the new source code. Should I be following this same approach or is there some other more idiomatic way in Red ?
I've experimented with using collect/keep in my parse rules to return a block of nested blocks, which in effect forms the AST. Another approach would be to save data into specific objects representing the different statements etc.
I'm still getting to grips with collect/keep, as to when a new block will be created and what will be kept. I'd also like to keep my parser rules as "clean" as possible, with as little other code intertwined in it. So I'm still not sure how best to add in Red code in round brackets in the parse rules. Adding code too early can cause the Red code to get executed, even if the rule eventually fails. Adding code too late means the code may not be executed in the order you expect, especially when dealing with multi-level statements like if, which can contain other statements.
So, specifically, any help on how to translate my example DSL to Red source code would be appreciated. Also any links to implementing DSLs like this in Red or Rebol would be great ! :)
Here are my parse rules :-
Red [
Purpose: example rules for parsing a simple language
]
SimpleLanguageParser: make object! [
Expr: [string! | integer! | block!]
Data: ['Person.AGE | 'Person.INCOME]
WriteMessageToLog: ['write 'message 'to 'log Expr]
SetData: ['set 'data Data '= Expr]
IfStatement: ['if Expr [any Statement] opt ['else [any Statement]] 'endif]
Statement: [WriteMessageToLog | SetData | IfStatement]
Rule: [
'rule word!
[any Statement]
'endrule
]
AnySimpLeLanguage: [Rule | [any Statement]]
]
SL: function [slInput] [
parse slInput SimpleLanguageParser/AnySimpleLanguage
]
An example of some source in the DSL :-
RULE TooYoung
IF [Person.Age < 15]
WRITE MESSAGE TO LOG "too young to earn an income"
SET DATA Person.Income = 0
ELSE
WRITE MESSAGE TO LOG "old enough"
ENDIF
ENDRULE
Translated to Red source code :-
TooYoung: function [] [
either Person.Age < 15 [
WriteMessageToLog "too young to earn an income"
Person.Income: 0
] [
WriteMessageToLog "old enough"
]
]
The data, ie Person.Age, Person.Income, and the function WriteMessageToLog are all things which would have been previously defined.
Note, for simplicity I've left Expr as block! etc, rather than defining Expr in any more detail in the DSL itself. Also, setting Person.Income in the function doesn't work as coded as it sets a local - but that's ok for now :)
Always nice to see someone digging language-oriented programming, keep it up and welcome to Red! ;)
Specifying correct grammar rules is the trickiest part of the job, and you've already nailed that. What's left is to intersperse your PEG (parsing expression grammar) with set, copy, collect/keep combo and paren! expressions in the right places, and then either create an AST from that or, in simplier cases, emit code directly.
Example
Here's a quickly baked (and definitely buggy!) example of how I'd tackled your task. Basically, it's slightly reworked code of yours, where matched patterns are setted, copyed or collected, and then bounded to specific words, which then just pasted into "template" (compose function inside emit-rule) to produce a Red code.
It's not the only way, I believe. #rebolek might come up with more industrial-strength solution, as he has experience with sophisticated parsers, which I'm lacking :P
Followup
As for if/else dilemma, I followed the approach proposed above -- instead of using opt I wrapped rule for else-branch into block and added an alternative match, which just sets false-block to none.
What to use for AST -- anything that allow to express a hierarchical structure, which is either a block! (though for performance gain you might want to use hash! or map!) or an object!. The advantage of object! is that it provides a context to be bound to, but here we're approaching a realm of so-called Bindology ("scoping" rules of Red language), which is another beast :)
Emitting C# code would be harder, but doable -- you'll need to assemble a string instead of Red code. I think, however, that, as a newcomer, you should stick with parsing directly at block-level (the way you done in your example), because it a lot easier and much expressive.
Another interesting (but much hairy) approach would be to re-define all words used in your DSL-block to work as you want.
Resources
We have a wiki entry about Red/Rebol dialects on github, which you might find if not useful, but interesting to read.
Also, two articles (this and this) in Red blog, I think you skimmed over first one already (if not, you should!).
Last, but not least, an exhaustive review of Parse principles and keywords (which has a couple of wrong parts in it though, so, caveat emptor). It's written for Rebol, but you should adapt examples to Red rather easily.
As a relative newcomer to the language, I do agree that there's a lack of examples and tutorials about DSL development, but we're working on that (at least in our heads) :)
Taking 9214's answer as a starting point, I've coded one possible solution. My approach has been :-
try to keep the parse rules as "clean" as possible
use collect and keep to return a block as the result, rather than trying to build a more complex AST
do some minimal translation in the keeps
the resulting block should be valid Red code
which uses predefined functions, where any more complex processing needs to happen
Most simple statements are easily translated to functions eg WRITE MESSAGE TO LOG becomes SL_WriteMessageToLog which can then do whatever it needs to do.
More complicated statements with structure, eg If/Else become functions which take block parameters which can then process the blocks as required.
For the If/Else complication, I've made this into two separate functions, SL_If and SL_Else. SL_If stores the result of the condition in a sequence, and SL_Else checks the latest result and removes it. This allows for nested If/Elses.
The presence of the final endrule can be checked for to ensure the input was correctly parsed. Once this is removed, we should have a valid function definition.
Here's the code :-
Red [
Purpose: example rules for parsing and translating a simple language
]
; some data
Person.AGE: 0
Person.INCOME: 0
; functions to implement some simple SL statements
SL_WriteMessageToLog: function [value] [
print value
]
SL_SetData: function [parmblock] [
field: parmblock/1
value: parmblock/2
if type? value = word! [
value: do value
]
print ["old value" field "=" do field]
set field value
print ["new value" field "=" do field]
]
; hold the If condition results, to be used to determine whether or not to do Else
IfConditionResults: []
SL_If: function [cond stats] [
cond_result: do cond
head insert IfConditionResults cond_result
if cond_result stats
]
SL_Else: function [stats] [
cond_result: first IfConditionResults
remove IfConditionResults
if not cond_result stats
]
; parsing rules
SimpleLanguageParser: make object! [
Expr: [logic! | string! | integer! | block!]
Data: ['Person.AGE | 'Person.INCOME]
WriteMessageToLog: ['write 'message 'to 'log set x Expr keep ('SL_WriteMessageToLog) keep (x)]
SetData: ['set 'data set d Data '= set x Expr keep ('SL_SetData) keep (reduce [d x])]
IfStatement: ['if keep ('SL_If) keep Expr collect [any Statement] opt ['else keep ('SL_Else) collect [any Statement]] 'endif]
Statement: [WriteMessageToLog | SetData | IfStatement]
Rule: [collect [
'rule set fname word! keep (to set-word! fname) keep ('does)
collect [any Statement]
keep 'endrule
]
]
AnySimpLeLanguage: [Rule | [any Statement]]
]
SL: function [slInput] [
parse slInput SimpleLanguageParser/Rule
]
For the example in the original post, the output is :-
TooYoung: does [
SL_If [Person.Age < 15] [
SL_WriteMessageToLog "too young to earn an income"
SL_SetData [Person.Income 0]
]
SL_Else [
SL_WriteMessageToLog "old enough"
]
]
ENDRULE
Thanks for your help to get this far.
Feedback on this approach and solution would be appreciated :)
Rebol2 has an /ANY refinement on the FIND function that can do wildcard searches:
>> find/any "here is a string" "s?r"
== "string"
I use this extensively in tight loops that need to perform well. But the refinement was removed in Rebol3.
What's the most efficient way of doing this in Rebol3? (I'm guessing a parse solution of some sort.)
Here's a stab at handling the "*" case:
like: funct [
series [series!]
search [series!]
][
rule: copy []
remove-each s b: parse/all search "*" [empty? s]
foreach s b [
append rule reduce ['to s]
]
append rule [to end]
all [
parse series rule
find series first b
]
]
used as follows:
>> like "abcde" "b*d"
== "bcde"
I had edited your question for "clarity" and changed it to say 'was removed'. That made it sound like it was a deliberate decision. Yet it actually turns out it may just not have been implemented.
BUT if anyone asks me, I don't think it should be in the box...and not just because it's a lousy use of the word "ALL". Here's why:
You're looking for patterns in strings...so if you're constrained to using a string to specify that pattern you get into "meta" problems. Let's say I want to extract the word *Rebol* or ?Red?, now there has to be escaping and things get ugly all over again. Back to RegEx. :-/
So what you might actually want isn't a STRING! pattern like s?r but a BLOCK! pattern like ["s" ? "r"]. This would permit constructs like ["?" ? "?"] or [{?} ? {?}]. That's better than rehashing the string hackery that every other language uses.
And that's what PARSE does, albeit in a slightly-less-declarative way. It also uses words instead of symbols, as Rebol likes to do. [{?} skip {?}] is a match rule where skip is an instruction that moves the parse position past any single element of the parse series between the question marks. It could also do so if it were parsing a block as input, and would match [{?} 12-Dec-2012 {?}].
I don't know entirely what the behavior of /ALL would-or-should be with something like "ab??cd e?*f"... if it provided alternate pattern logic or what. I'm assuming the Rebol2 implementation is brief? So likely it only matches one pattern.
To set a baseline, here's a possibly-lame PARSE solution for the s?r intent:
>> parse "here is a string" [
some [ ; match rule repeatedly
to "s" ; advance to *before* "s"
pos: ; save position as potential match
skip ; now skip the "s"
[ ; [sub-rule]
skip ; ignore any single character (the "?")
"r" ; match the "r", and if we do...
return pos ; return the position we saved
| ; | (otherwise)
none ; no-op, keep trying to match
]
]
fail ; have PARSE return NONE
]
== "string"
If you wanted it to be s*r you would change the skip "r" return pos into a to "r" return pos.
On an efficiency note, I'll mention that it is indeed the case that characters are matched against characters faster than strings. So to #"s" and #"r" to end make a measurable difference in the speed when parsing strings in general. Beyond that, I'm sure others can do better.
The rule is certainly longer than "s?r". But it's not that long when comments are taken out:
[some [to #"s" pos: skip [skip #"r" return pos | none]] fail]
(Note: It does leak pos: as written. Is there a USE in PARSE, implemented or planned?)
Yet a nice thing about it is that it offers hook points at all the moments of decision, and without the escaping defects a naive string solution has. (I'm tempted to give my usual "Bad LEGO alligator vs. Good LEGO alligator" speech.)
But if you don't want to code in PARSE directly, it seems the real answer would be some kind of "Glob Expression"-to-PARSE compiler. It might be the best interpretation of glob Rebol would have, because you could do a one-off:
>> parse "here is a string" glob "s?r"
== "string"
Or if you are going to be doing the match often, cache the compiled expression. Also, let's imagine our block form uses words for literacy:
s?r-rule: glob ["s" one "r"]
pos-1: parse "here is a string" s?r-rule
pos-2: parse "reuse compiled RegEx string" s?r-rule
It might be interesting to see such a compiler for regex as well. These also might accept not only string input but also block input, so that both "s.r" and ["s" . "r"] were legal...and if you used the block form you wouldn't need escaping and could write ["." . "."] to match ".A."
Fairly interesting things would be possible. Given that in RegEx:
(abc|def)=\g{1}
matches abc=abc or def=def
but not abc=def or def=abc
Rebol could be modified to take either the string form or compile into a PARSE rule with a form like:
regex [("abc" | "def") "=" (1)]
Then you get a dialect variation that doesn't need escaping. Designing and writing such compilers is left as an exercise for the reader. :-)
I've broken this into two functions: one that creates a rule to match the given search value, and the other to perform the search. Separating the two allows you to reuse the same generated parse block where one search value is applied over multiple iterations:
expand-wildcards: use [literal][
literal: complement charset "*?"
func [
{Creates a PARSE rule matching VALUE expanding * (any characters) and ? (any one character)}
value [any-string!] "Value to expand"
/local part
][
collect [
parse value [
; empty search string FAIL
end (keep [return (none)])
|
; only wildcard return HEAD
some #"*" end (keep [to end])
|
; everything else...
some [
; single char matches
#"?" (keep 'skip)
|
; textual match
copy part some literal (keep part)
|
; indicates the use of THRU for the next string
some #"*"
; but first we're going to match single chars
any [#"?" (keep 'skip)]
; it's optional in case there's a "*?*" sequence
; in which case, we're going to ignore the first "*"
opt [
copy part some literal (
keep 'thru keep part
)
]
]
]
]
]
]
like: func [
{Finds a value in a series and returns the series at the start of it.}
series [any-string!] "Series to search"
value [any-string! block!] "Value to find"
/local skips result
][
; shortens the search a little where the search starts with a regular char
skips: switch/default first value [
#[none] #"*" #"?" ['skip]
][
reduce ['skip 'to first value]
]
any [
block? value
value: expand-wildcards value
]
parse series [
some [
; we have our match
result: value
; and return it
return (result)
|
; step through the string until we get a match
skips
]
; at the end of the string, no matches
fail
]
]
Splitting the function also gives you a base to optimize the two different concerns: finding the start and matching the value.
I went with PARSE as even though *? are seemingly simple rules, there is nothing quite as expressive and quick as PARSE to effectively implementing such a search.
It might yet as per #HostileFork to consider a dialect instead of strings with wildcards—indeed to the point where Regex is replaced by a compile-to-parse dialect, but is perhaps beyond the scope of the question.
I want to make use of Maxima as the backend to solve some computations used in my LaTeX input file.
I did the following steps.
Step 1
Download and install Maxima.
Step 2
Create a batch file named cas.bat (for example) as follows.
rem cas.bat
echo off
set PATH=%PATH%;"C:\Program Files (x86)\Maxima-5.31.2\bin"
maxima --very-quiet -r %1 > solution.tex
Save the batch in the same directory in which your input file below exists. It is just for the sake of simplicity.
Step 3
Create the input file named main.tex (for example) as follows.
% main.tex
\documentclass[preview,border=12pt,12pt]{standalone}
\usepackage{amsmath}
\def\f(#1){(#1)^2-5*(#1)+6}
\begin{document}
\section{Problem}
Evaluate $\f(x)$ for $x=\frac 1 2$.
\section{Solution}
\immediate\write18{cas "x: 1/2;tex(\f(x));"}
\input{solution}
\end{document}
Step 4
Compile the input file with pdflatex -shell-escape main and you will get a nice output as follows.
!
Step 5
Done.
Questions
Apparently the output of Maxima is as follows. I don't know how to make it cleaner.
solution.tex
1
-
2
$${{15}\over{4}}$$
false
Now, my question are
how to remove such texts?
how to obtain just \frac{15}{4} without $$...$$?
(1) To suppress output, terminate input expressions with dollar sign (i.e. $) instead of semicolon (i.e. ;).
(2) To get just the TeX-ified expression sans the environment delimiters (i.e. $$), call tex1 instead of tex. Note that tex1 returns a string, which you have to print yourself (while tex prints it for you).
Combining these ideas with the stuff you showed, I think your program could look like this:
"x: 1/2$ print(tex1(\f(x)))$"
I think you might find the Maxima mailing list helpful. I'm pretty sure there have been several attempts to create a system such as the one you describe. You can also look at the documentation.
I couldn't find any way to completely clean up Maxima's output within Maxima itself. It always echoes the input line, and always writes some whitespace after the output. The following is an example of a perl script that accomplishes the cleanup.
#!/usr/bin/perl
use strict;
my $var = $ARGV[0];
my $expr = $ARGV[1];
sub do_maxima_to_tex {
my $m = shift;
my $c = "maxima --batch-string='exptdispflag:false; print(tex1($m))\$'";
my $e = `$c`;
my #x = split(/\(%i\d+\)/,$e); # output contains stuff like (%i1)
my $f = pop #x; # remove everything before the echo of the last input
while ($f=~/\A /) {$f=~s/\A .*\n//} # remove echo of input, which may be more than one line
$f =~ s/\\\n//g; # maxima breaks latex tokens in the middle at end of line; fix this
$f =~ s/\n/ /g; # if multiple lines, get it into one line
$f =~ s/\s+\Z//; # get rid of final whitespace
return $f;
}
my $e1 = do_maxima_to_tex("diff($expr,$var,1)");
my $e2 = do_maxima_to_tex("diff($expr,$var,2)");
print <<TEX;
The first derivative is \$$e1\$. Differentiating a second time,
we get \$$e2\$.
TEX
If you name this script a.pl, then doing
a.pl z 3*z^4
outputs this:
The first derivative is $12\,z^3$. Differentiating a second time,
we get $36\,z^2$.
For the OP's application, a script like this one could be what is invoked by the write18 in the latex file.
If you really want to use LaTeX then the maxiplot package is the answer. It provides a maxima environment inside of which you enter Maxima commands. When you process your LaTeX file a Maxima batch file is generated. Process this file with Maxima and process your LaTeX file again to typeset the equations generated by Maxima.
If you would rather have 2D math input with live typesetting then use TeXmacs. It is a cross-platform document authoring environment (a word processor on steroids if you like) that includes plugins for Maxima, Mathematica and many more scientific computing tools. If you need to or are not satisfied with the typesetting, you can export your document to LaTeX.
I know this is a very old post. Excellent answers for the question asked by OP. I was using --very-quiet -r options on the command line for a long time like OP, but in maxima version 5.43.2 they behave differently. See maxima command line v5.43 is behaving differently than v5.41. I am answering this question with a cross reference because when incorporating these answers in your solutions, make sure the changes in behavior of those command line flags are also incorporated.