On Mon, 9 Feb 2015, Sebastien Vauban wrote:
"Charles C. Berry" wrote:
On Fri, 23 Jan 2015, Sebastien Vauban wrote:
"Charles C. Berry" wrote:
Sebastien Vauban wrote:
In a long document, I must have ":eval no" at file level, as this
is the common setting for most code blocks. However, how do I unset
that for some call lines.
I don't get why one has to add ":eval yes" for both types of headers
arguments.
I still don't get that: why do I need to add *twice* ":eval yes", in
both the "inside header args" and the "end header args"?
The documentation [1] states:
┌────
│ END HEADER ARGUMENTS are applied to the calling instance and DO NOT
│ AFFECT EVALUATION OF THE NAMED CODE BLOCK. They affect how the
│ results are incorporated into the Org mode buffer and how the call
│ line is exported.
└────
If end header args don't affect the evaluation of the name code block,
why do we have to set ":eval" to "yes", then?
Because there are two evaluations to be made of a call_abc() instance or a
`#BEGIN_SRC lang :var x=abc() ...' instance:
1. one of abc()
2. one of the instance.
They can be made in any of the four combinations of `:eval yes' and `:eval
no'. See below for an example of a src block calling another using the
`:var x=abc()' idiom.
Moreover, I once read that when evaluating a call line, it is
converted into an ephemeral Emacs Lisp code block equivalent to the
call line (and created at the point of the call line):
#+begin_src emacs-lisp :var result=<NAME>(<ARGUMENTS>) <INSIDE-HEADER-ARGS>
result
#+end_src
which is evaluated in place.
No, like this:
#+begin_src emacs-lisp :var result=<NAME>[<INSIDE-HEADER-ARGS>](<ARGUMENTS>)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
What's that syntax? The one described for "header arguments in function
calls"? Aren't we recursive here: describing syntax equivalent to
a call via the ephemeral code block, reusing syntax for a call?
Not sure how best to answer. Maybe try out all combos to demo what
happens:
A simple src block:
#+NAME: up
#+BEGIN_SRC emacs-lisp :var x="CbA"
(upcase x)
#+END_SRC
Eval this src block and `up' - prompted twice for evalution upon
execution. Note RESULTS == 'C B A':
#+BEGIN_SRC emacs-lisp :eval yes :var x=up[:eval yes](x="c b a")
x
#+END_SRC
#+RESULTS:
: C B A
Do not eval this src block but eval `up' - prompted to evaluate `up'
and message that evaluation is disabled appears for current src
block. No RESULTS:
#+BEGIN_SRC emacs-lisp :eval no :var x=up[:eval yes](x="c b a")
x
#+END_SRC
Eval this src block and not `up' - prompted once for evaluation. Note
RESULTS == 'nil', as x did not get a value assigned to it:
#+BEGIN_SRC emacs-lisp :eval yes :var x=up[:eval no](x="c b a")
x
#+END_SRC
#+RESULTS:
: nil
Eval neither. No prompts. No result.
#+BEGIN_SRC emacs-lisp :eval no :var x=up[:eval no](x="c b a")
x
#+END_SRC
Where do <END-HEADER-ARGS> fit into that picture?
Either before or after the :var ...
Maybe better to say:
In this context the equivalent of <END-HEADER-ARGS> is the `:eval'
header for the src block, which can go anywhere on the line. The
<END-HEADER-ARGS> if supplied in this context seem to be ignored.
HTH,
Chuck