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authorHans Bolinder <[email protected]>2016-12-05 09:48:59 +0100
committerHans Bolinder <[email protected]>2016-12-05 09:48:59 +0100
commit210658e7271a7f1e62721a6ff6d77aa52586e31d (patch)
tree62c391090334cadd364a3578f8095d3bf4000e82 /lib/stdlib
parent64ec4354a990460dfa5274bf220e29dfeb1029f0 (diff)
parent45106f76360c7db585479726789f9d91a8027e2c (diff)
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Merge branch 'richcarl/stdlib/io_lib_pretty-comments/PR-1228'
* richcarl/stdlib/io_lib_pretty-comments/PR-1228: Add comments for understanding io_lib_pretty
Diffstat (limited to 'lib/stdlib')
-rw-r--r--lib/stdlib/src/io_lib_format.erl3
-rw-r--r--lib/stdlib/src/io_lib_pretty.erl20
2 files changed, 22 insertions, 1 deletions
diff --git a/lib/stdlib/src/io_lib_format.erl b/lib/stdlib/src/io_lib_format.erl
index 1da866dc88..c7b75961cb 100644
--- a/lib/stdlib/src/io_lib_format.erl
+++ b/lib/stdlib/src/io_lib_format.erl
@@ -343,7 +343,8 @@ term(T, F, Adj, P0, Pad) ->
%% print(Term, Depth, Field, Adjust, Precision, PadChar, Encoding,
%% Indentation)
-%% Print a term.
+%% Print a term. Field width sets maximum line length, Precision sets
+%% initial indentation.
print(T, D, none, Adj, P, Pad, E, Str, I) ->
print(T, D, 80, Adj, P, Pad, E, Str, I);
diff --git a/lib/stdlib/src/io_lib_pretty.erl b/lib/stdlib/src/io_lib_pretty.erl
index 16ca2f41dc..94376408d1 100644
--- a/lib/stdlib/src/io_lib_pretty.erl
+++ b/lib/stdlib/src/io_lib_pretty.erl
@@ -97,31 +97,42 @@ print(Term, Col, Ll, D, RecDefFun) ->
print(Term, Col, Ll, D, M, RecDefFun) ->
print(Term, Col, Ll, D, M, RecDefFun, latin1, true).
+%% D = Depth, default -1 (infinite), or LINEMAX=30 when printing from shell
+%% Col = current column, default 1
+%% Ll = line length/~p field width, default 80
+%% M = CHAR_MAX (-1 if no max, 60 when printing from shell)
print(_, _, _, 0, _M, _RF, _Enc, _Str) -> "...";
print(Term, Col, Ll, D, M, RecDefFun, Enc, Str) when Col =< 0 ->
+ %% ensure Col is at least 1
print(Term, 1, Ll, D, M, RecDefFun, Enc, Str);
print(Term, Col, Ll, D, M0, RecDefFun, Enc, Str) when is_tuple(Term);
is_list(Term);
is_map(Term);
is_bitstring(Term) ->
+ %% preprocess and compute total number of chars
If = {_S, Len} = print_length(Term, D, RecDefFun, Enc, Str),
+ %% use Len as CHAR_MAX if M0 = -1
M = max_cs(M0, Len),
if
Len < Ll - Col, Len =< M ->
+ %% write the whole thing on a single line when there is room
write(If);
true ->
+ %% compute the indentation TInd for tagged tuples and records
TInd = while_fail([-1, 4],
fun(I) -> cind(If, Col, Ll, M, I, 0, 0) end,
1),
pp(If, Col, Ll, M, TInd, indent(Col), 0, 0)
end;
print(Term, _Col, _Ll, _D, _M, _RF, _Enc, _Str) ->
+ %% atomic data types (bignums, atoms, ...) are never truncated
io_lib:write(Term).
%%%
%%% Local functions
%%%
+%% use M only if nonnegative, otherwise use Len as default value
max_cs(M, Len) when M < 0 ->
Len;
max_cs(M, _Len) ->
@@ -153,6 +164,7 @@ pp({S, _Len}, _Col, _Ll, _M, _TInd, _Ind, _LD, _W) ->
%% Print a tagged tuple by indenting the rest of the elements
%% differently to the tag. Tuple has size >= 2.
pp_tag_tuple([{Tag,Tlen} | L], Col, Ll, M, TInd, Ind, LD, W) ->
+ %% this uses TInd
TagInd = Tlen + 2,
Tcol = Col + TagInd,
S = $,,
@@ -207,6 +219,7 @@ pp_field({{field, Name, NameL, F}, _Len}, Col0, Ll, M, TInd, Ind0, LD, W0) ->
{[Name, " = ", S | pp(F, Col, Ll, M, TInd, Ind, LD, W)], Ll}. % force nl
rec_indent(RInd, TInd, Col0, Ind0, W0) ->
+ %% this uses TInd
Nl = (TInd > 0) and (RInd > TInd),
DCol = case Nl of
true -> TInd;
@@ -285,6 +298,7 @@ pp_binary(S, N, _N0, Ind) ->
S
end.
+%% write the whole thing on a single line
write({{tuple, _IsTagged, L}, _}) ->
[${, write_list(L, $,), $}];
write({{list, L}, _}) ->
@@ -344,8 +358,10 @@ print_length({}, _D, _RF, _Enc, _Str) ->
print_length(#{}=M, _D, _RF, _Enc, _Str) when map_size(M) =:= 0 ->
{"#{}", 3};
print_length(List, D, RF, Enc, Str) when is_list(List) ->
+ %% only flat lists are "printable"
case Str andalso printable_list(List, D, Enc) of
true ->
+ %% print as string, escaping double-quotes in the list
S = write_string(List, Enc),
{S, length(S)};
%% Truncated lists could break some existing code.
@@ -401,6 +417,7 @@ print_length(<<_/bitstring>>=Bin, D, _RF, Enc, Str) ->
end;
print_length(Term, _D, _RF, _Enc, _Str) ->
S = io_lib:write(Term),
+ %% S can contain unicode, so iolist_size(S) cannot be used here
{S, lists:flatlength(S)}.
print_length_map(_Map, 1, _RF, _Enc, _Str) ->
@@ -483,6 +500,7 @@ list_length_tail({_, Len}, Acc) ->
%% ?CHARS printable characters has depth 1.
-define(CHARS, 4).
+%% only flat lists are "printable"
printable_list(_L, 1, _Enc) ->
false;
printable_list(L, _D, latin1) ->
@@ -736,9 +754,11 @@ while_fail([], _F, V) ->
while_fail([A | As], F, V) ->
try F(A) catch _ -> while_fail(As, F, V) end.
+%% make a string of N spaces
indent(N) when is_integer(N), N > 0 ->
chars($\s, N-1).
+%% prepend N spaces onto Ind
indent(1, Ind) -> % Optimization of common case
[$\s | Ind];
indent(4, Ind) -> % Optimization of common case