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Code Cleanup

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- Removed obsolete parser info.
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Paul Beckingham 2014-02-08 10:42:49 -05:00
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commit 7ec24658b5
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94
doc/misc/parser/README
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The main focus of the 2.4.0 release is a new command line parser that has more
capabilities with fewer quirks and bugs.
Improvements needed:
- Assorted quoting issues. If this command is issued, then the quoting should
be obeyed:
task add one project:'Bob\'s Project'
task add "one 'two' three"
task add 'one "two" three'
task add 'one \'two\' three'
task add "one \"two\" three"
- The process of splitting and rejoining tokens causes this kind of problem:
"one (two) three" --> "one ( two) three"
- Any formatting in the input that makes it past the shell should be preserved.
- The '--' token should faithfully cause no further parsing - lexing only.
- The ability to perform simple math:
task add one due:eoy wait:due-2wks scheduled:wait-1wk
When processed left to right, this command has referential integrity.
- An attribute value must be a single argument, but can be presented in several
equivalent ways:
wait:due-2wks
wait:'due-2wks'
wait:"due-2wks'
wait:"due -2wks'
wait:"due - 2wks'
wait:due\ -\ 2wks
Grammar:
To achieve the above, a formal grammar will be developed, otherwise a hand-
crafted parser is going to be unmaintainable. See the grammar.txt file for the
formal definition.
This grammar.txt will be embedded into task as a single-string document, then
itself parsed and used. This has several advantages:
- It allows the grammar to be discussed in its purest form, with an
authoritative document as a definition.
- It allows the grammar to be tweaked at a high level without code changes.
- It allows a developer to experiment with grammar.
Expressions:
The expression evaluator will be capable of applying any supported filter.
The expression evaluator will also be capable of evaluating fragments of output
from the parser, yielding a single value. As an example, the command line:
task add one due:eoy wait:due-2wks
Is to be parsed as:
index | 0 1 2 3 4
--------+-----------------------------------------------
raw | task add one due:eoy wait:due-2wks
type | command string attr attr
subtype | read
attr | desc due wait
value | eval 'eoy' eval 'due-2wks'
The eval needs of this command are:
'eoy' == date literal
'due-2wks' == <dom> - <duration>
The parse tree should be:
+- add COMMAND
+- "one" WORD
+- attr
| +- due ATTRIBUTE
| +- expr
| | + "eoy" LITERAL DATE
+- attr
+- wait ATTRIBUTE
+- expr
+= "due" DOM DATE
+= "-" OP
+= "2wks" LITERAL DURATION

34
doc/misc/parser/expressions.txt
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The expression evaluator allows powerful filters and modifications.
There are four data types, just like UDAs:
string project, description
date due, wait ...
duration recur
numeric urgency
There are several forms of literals:
rc.name configuration
<dom> task-specific data
<numeric> numbers
<date> either ISO-8601 or rc.dateformat dates
<duration> either ISO-8601 or durations
There are many supported operators:
+ addition, concatenation
- subtraction, unary minus
* multiplication
/ division
( ) precedence
and or xor not ! logical operators
< <= > >= relation operators
= != equality operators
~ !~ match operators
There are helper operators to perform odd operations:
__hastag__ presence of a tag
__notag__ absence of a tag

79
doc/misc/parser/grammar.txt
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# The command line needs to obey a grammar. It is then against this grammar
# that bugs will be identified.
#
# Conventions:
# - Literals are always double-quoted.
# - "*", "+" and "?" suffixes have POSIX semantics.
# - Low-level primitives are in <brackets>.
# - @reports for dynamic lists such as custom report names.
#
# The general form of commands is:
# task [ all-commands ]
#
grammar ::= all-commands?
;
all-commands ::= custom-report
| read-command
| write-command
| special-command
;
custom-report ::= filter? @report ;
read-command ::= filter? @readcmd ;
write-command ::= filter? @writecmd modifiers ;
special-command ::= ;
filter ::= expression ;
expression ::= ;
modifiers ::= ;
# Low-level:
dom ::= context-value
| system-value
| rc-value
| task-value
;
context-value ::= "context.program"
| "context.args"
| "context.width"
| "context.height"
;
system-value ::= "system.version"
| "system.os"
;
rc-value ::= /rc\.[a-zA-Z.]+/
;
task-value ::= <id> "." attribute
| <uuid> "." attribute
;
literal ::= <string>
| <numeric>
| <date>
| <duration>
;
# Supported primitives:
#
# <id>
# <uuid>
# <override>
# <string>
# <numeric>
# <date>
# <duration>
# @command all commands
# @report all custom reports
# @attributes all attributes, UDAs
# @readcmd all read-only commands
# @writecmd all write commands