Hi Peter,
almost correct. The first comment should be "// may point to an optional
string typically containing 6 spaces".
prompt can be 0 and then no prompt is printed. Otherwise the function
pushes the prompt (backwards)
back into stdin. Whether that works is a matter of the underlying
operating system. The man page
of ungetc() says that only 1 ungetc() char is guaranteed but we push 6.
Another question is whether
an ungetc() into stdin will occur on C++ cin?
The main use case for this were scripts where it does not matter too
much if a prompt is printed
or not. Note also that pushing chars back into stdin has a different
effect than just printing the prompt
- there are cases where the prompt should be editable (⍞ I believe).
/// Jürgen
On 06/01/2014 04:22 AM, Peter Teeson wrote:
Hi Jürgen:
Well please help me properly understand the no_readline function in
Input.cc.
Because it's called instead of the readline library because of the
--rawCIN.
I've made comments of my interpretation of the code but am probably wrong.
So I'd appreciate any contribution to my very rusty C++.
no_readline(const UCS_string * prompt)
{
if (prompt)// points at 6 spaces x'20'
{
CIN << '\r' << *prompt << flush;// CIN is an ostream see Output.cc
UTF8_string prompt_utf(*prompt);
loop(p, prompt_utf.size())// ungets those spaces from stdin
{
const int cc = prompt_utf[prompt_utf.size() - p - 1];
ungetc(cc & 0xFF, stdin);
}
}
etc
Much appreciated and
respect…
Peter
On 2014-05-31, at 11:13 AM, Juergen Sauermann
<juergen.sauerm...@t-online.de <mailto:juergen.sauerm...@t-online.de>>
wrote:
Hi Peter,
looks OK to me. (Note: as of recently *apl -s* does the same as your
command line options).
--rawCIN reads directly from the file (stdin in this case) without
outputting any prompts.
The line numbers in the ∇-editor count as prompts and are therefore
suppressed as well.
However when you display the function with [⎕] then the line numbers
are not prompts
but output of the editor.
/// Jürgen
