printf.xgml

<?xml version="1.0"?>
<!--
  Provides a way to print formatted text to stdout.
  Always prints a newline after the output.

  Example:
    usereg {Martin} !name 1992 !year-of-birth
    [
      ;name
      2012 ;year-of-birth sub
      {England}
    ] {Hello {~1} from {~3} -- you are (at least) {~2} years old} printf

  Escape Sequences:
  ; : ! . and % are illegal in the format specifier, instead use:
    {~dot}   .
    {~dots}  ...
    {~excl}  !
    {~colon} :
    {~semi}  ;
    {~perc}  %
    {~nl}    newline
  These require that your terminal handles ^H correctly (i.e. deletes the previous character).
-->
<Library name="printf-lib">
<item id="_depends" exec="0"><![CDATA[
"lib/short-circuit.xgml"
"lib/switch.xgml"
]]></item>
<item id="printf" exec="1"><![CDATA[
usereg !fmt !args
% TODO: [...] x bsearch -> :I
% [ /~1 /~2 ... /~n ] ;token bsearch
{
  usereg !array
  ;array 0 get cvlit [
    /~1  0   /~2  1   /~3  2   /~4  3   /~5  4
    /~6  5   /~7  6   /~8  7   /~9  8   /~10 9
    -1
  ] switch
} !placeholder-index

;fmt {
  !token
  ;token type /Array eq {
    ;token length 1 eq { ;token :placeholder-index -1 ne } and* {
      % Arrays containing a placeholder are substituted for the corresponding argument.
      ;args ;token :placeholder-index get (0,0) tokenformat
    } {
      % Escape sequences are printed with backspaces (^H) embedded to remove quotes.
      % HINT: Abusing and*, we know the switch will default if passed a 0.
      ;token length 0 gt { ;token 0 get } and* cvlit [
        /~dots  {"..."} cvlit
        /~dot   {"."} cvlit
        /~excl  {"!"} cvlit
        /~colon {":"} cvlit
        /~semi  {";"} cvlit
        /~perc  {"%"} cvlit
        { ;token 1 array }
      ] switch
    } ifelse
  } {
    % Non-arrays are printed without change.
    % TODO: Should we tokenformat each element of the array?
    ;token
  } ifelse
} map flatten echo
]]></item>
</Library>