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How to explain the behaviour of TreeForm?

With/Function(/etc) replacement behaviourdirect assignment to the element in a TableSome _atomic elements' TreeForm looks confusing with Level in appearanceConverting expressions to “edges” for use in TreePlot, GraphTreeForm expression that will automatically spread nodes vertically so labels do not overlapInserting symbols' definitions during read time of the codeUnderstanding the output formatting of held formsHow to stop TreeForm from shaking when changing resolution?Strange behaviour of ValueQ inside loopsStrange behaviour (or issue?) in using evaluation of held argument inside a table in Mathematica

7

$begingroup$

Just try this:

g=1;a=1;TreeForm[Hold[g[a]]]

The weird thing in the outcome is that the node of g displays 1 ,and a is still a.
I do not know how to explain the behaviour of TreeForm.

evaluation hold trees

share|improve this question

edited Apr 30 at 16:23

user64494

3,67911222

asked Apr 30 at 13:46

任天一任天一

1397

$endgroup$

add a comment | 

7

$begingroup$

Just try this:

g=1;a=1;TreeForm[Hold[g[a]]]

The weird thing in the outcome is that the node of g displays 1 ,and a is still a.
I do not know how to explain the behaviour of TreeForm.

evaluation hold trees

share|improve this question

edited Apr 30 at 16:23

user64494

3,67911222

asked Apr 30 at 13:46

任天一任天一

1397

$endgroup$

add a comment | 

$begingroup$

Just try this:

g=1;a=1;TreeForm[Hold[g[a]]]

The weird thing in the outcome is that the node of g displays 1 ,and a is still a.
I do not know how to explain the behaviour of TreeForm.

evaluation hold trees

share|improve this question

edited Apr 30 at 16:23

user64494

3,67911222

asked Apr 30 at 13:46

任天一任天一

1397

$endgroup$

g=1;a=1;TreeForm[Hold[g[a]]]

share|improve this question

edited Apr 30 at 16:23

user64494

3,67911222

asked Apr 30 at 13:46

任天一任天一

1397

share|improve this question

edited Apr 30 at 16:23

user64494

3,67911222

asked Apr 30 at 13:46

任天一任天一

1397

edited Apr 30 at 16:23

user64494

3,67911222

edited Apr 30 at 16:23

user64494

3,67911222

asked Apr 30 at 13:46

任天一任天一

1397

asked Apr 30 at 13:46

任天一任天一

1397

2 Answers
2

active

oldest

votes

5

$begingroup$

I would call this a bug. Please report it to Wolfram.

IGraph/M's IGExpressionTree can handle this:

IGExpressionTree[Hold[g[a]]]

The documentation has examples that show how to get a more TreeForm-like output. Do keep in mind that the purpose of IGExpressionTree is not a perfect visualization of expressions, but simply converting fairly benign expressions to Graph (or rather to generate tree graphs which are easier to assemble as expressions). It is definitely possible to construct examples where it leaks evaluation, and I am not going to fix these if the fix would affect performance.

share|improve this answer

edited Apr 30 at 15:42

answered Apr 30 at 15:19

SzabolcsSzabolcs

166k15455961

$endgroup$

add a comment | 

3

$begingroup$

If the symbols with OwnValues are all on the context path, then one idea is to write the expression to a string or file, where contexts are not included, and then to block the context and context path so that all symbols are loaded in a temporary context. The symbols in the temporary context will not have OwnValues, so you can use TreeForm without worrying about leaky symbols.

There is one issue to deal with. The new symbols should only be temporary, which means the output should not contain any references to these symbols. The way to fix this is to convert the TreeForm output to boxes, and then remove the symbols before returning the TreeForm box output. I will use Export[..., "Text"] to convert the expression to a string, there may be better options:

sealedTreeForm[expr_] := With[es = ExportString[expr, "Text"],
 Block[$Context="FOO`", $ContextPath="System`", "FOO`",
 Internal`WithLocalSettings[
 Null,
 Quiet[
 RawBoxes @ ToBoxes @ TreeForm @ ImportString[es],
 General::shdw
 ],
 Remove["FOO`*"]
 ]
 ]
]

Example:

g=1; a=1; sealedTreeForm[Hold[g[a]]]

share|improve this answer

answered Apr 30 at 16:14

Carl WollCarl Woll

77.9k3102206

$endgroup$

add a comment | 

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5

$begingroup$

I would call this a bug. Please report it to Wolfram.

IGraph/M's IGExpressionTree can handle this:

IGExpressionTree[Hold[g[a]]]

The documentation has examples that show how to get a more TreeForm-like output. Do keep in mind that the purpose of IGExpressionTree is not a perfect visualization of expressions, but simply converting fairly benign expressions to Graph (or rather to generate tree graphs which are easier to assemble as expressions). It is definitely possible to construct examples where it leaks evaluation, and I am not going to fix these if the fix would affect performance.

share|improve this answer

edited Apr 30 at 15:42

answered Apr 30 at 15:19

SzabolcsSzabolcs

166k15455961

$endgroup$

add a comment | 

5

$begingroup$

I would call this a bug. Please report it to Wolfram.

IGraph/M's IGExpressionTree can handle this:

IGExpressionTree[Hold[g[a]]]

The documentation has examples that show how to get a more TreeForm-like output. Do keep in mind that the purpose of IGExpressionTree is not a perfect visualization of expressions, but simply converting fairly benign expressions to Graph (or rather to generate tree graphs which are easier to assemble as expressions). It is definitely possible to construct examples where it leaks evaluation, and I am not going to fix these if the fix would affect performance.

share|improve this answer

edited Apr 30 at 15:42

answered Apr 30 at 15:19

SzabolcsSzabolcs

166k15455961

$endgroup$

add a comment | 

$begingroup$

I would call this a bug. Please report it to Wolfram.

IGraph/M's IGExpressionTree can handle this:

IGExpressionTree[Hold[g[a]]]

The documentation has examples that show how to get a more TreeForm-like output. Do keep in mind that the purpose of IGExpressionTree is not a perfect visualization of expressions, but simply converting fairly benign expressions to Graph (or rather to generate tree graphs which are easier to assemble as expressions). It is definitely possible to construct examples where it leaks evaluation, and I am not going to fix these if the fix would affect performance.

share|improve this answer

edited Apr 30 at 15:42

answered Apr 30 at 15:19

SzabolcsSzabolcs

166k15455961

$endgroup$

IGExpressionTree[Hold[g[a]]]

share|improve this answer

edited Apr 30 at 15:42

answered Apr 30 at 15:19

SzabolcsSzabolcs

166k15455961

answered Apr 30 at 15:19

SzabolcsSzabolcs

166k15455961

answered Apr 30 at 15:19

SzabolcsSzabolcs

166k15455961

3

$begingroup$

If the symbols with OwnValues are all on the context path, then one idea is to write the expression to a string or file, where contexts are not included, and then to block the context and context path so that all symbols are loaded in a temporary context. The symbols in the temporary context will not have OwnValues, so you can use TreeForm without worrying about leaky symbols.

There is one issue to deal with. The new symbols should only be temporary, which means the output should not contain any references to these symbols. The way to fix this is to convert the TreeForm output to boxes, and then remove the symbols before returning the TreeForm box output. I will use Export[..., "Text"] to convert the expression to a string, there may be better options:

sealedTreeForm[expr_] := With[es = ExportString[expr, "Text"],
 Block[$Context="FOO`", $ContextPath="System`", "FOO`",
 Internal`WithLocalSettings[
 Null,
 Quiet[
 RawBoxes @ ToBoxes @ TreeForm @ ImportString[es],
 General::shdw
 ],
 Remove["FOO`*"]
 ]
 ]
]

Example:

g=1; a=1; sealedTreeForm[Hold[g[a]]]

share|improve this answer

answered Apr 30 at 16:14

Carl WollCarl Woll

77.9k3102206

$endgroup$

add a comment | 

3

$begingroup$

If the symbols with OwnValues are all on the context path, then one idea is to write the expression to a string or file, where contexts are not included, and then to block the context and context path so that all symbols are loaded in a temporary context. The symbols in the temporary context will not have OwnValues, so you can use TreeForm without worrying about leaky symbols.

There is one issue to deal with. The new symbols should only be temporary, which means the output should not contain any references to these symbols. The way to fix this is to convert the TreeForm output to boxes, and then remove the symbols before returning the TreeForm box output. I will use Export[..., "Text"] to convert the expression to a string, there may be better options:

sealedTreeForm[expr_] := With[es = ExportString[expr, "Text"],
 Block[$Context="FOO`", $ContextPath="System`", "FOO`",
 Internal`WithLocalSettings[
 Null,
 Quiet[
 RawBoxes @ ToBoxes @ TreeForm @ ImportString[es],
 General::shdw
 ],
 Remove["FOO`*"]
 ]
 ]
]

Example:

g=1; a=1; sealedTreeForm[Hold[g[a]]]

share|improve this answer

answered Apr 30 at 16:14

Carl WollCarl Woll

77.9k3102206

$endgroup$

add a comment | 

$begingroup$

If the symbols with OwnValues are all on the context path, then one idea is to write the expression to a string or file, where contexts are not included, and then to block the context and context path so that all symbols are loaded in a temporary context. The symbols in the temporary context will not have OwnValues, so you can use TreeForm without worrying about leaky symbols.

There is one issue to deal with. The new symbols should only be temporary, which means the output should not contain any references to these symbols. The way to fix this is to convert the TreeForm output to boxes, and then remove the symbols before returning the TreeForm box output. I will use Export[..., "Text"] to convert the expression to a string, there may be better options:

sealedTreeForm[expr_] := With[es = ExportString[expr, "Text"],
 Block[$Context="FOO`", $ContextPath="System`", "FOO`",
 Internal`WithLocalSettings[
 Null,
 Quiet[
 RawBoxes @ ToBoxes @ TreeForm @ ImportString[es],
 General::shdw
 ],
 Remove["FOO`*"]
 ]
 ]
]

Example:

g=1; a=1; sealedTreeForm[Hold[g[a]]]

share|improve this answer

answered Apr 30 at 16:14

Carl WollCarl Woll

77.9k3102206

$endgroup$

sealedTreeForm[expr_] := With[es = ExportString[expr, "Text"],
 Block[$Context="FOO`", $ContextPath="System`", "FOO`",
 Internal`WithLocalSettings[
 Null,
 Quiet[
 RawBoxes @ ToBoxes @ TreeForm @ ImportString[es],
 General::shdw
 ],
 Remove["FOO`*"]
 ]
 ]
]

g=1; a=1; sealedTreeForm[Hold[g[a]]]

share|improve this answer

answered Apr 30 at 16:14

Carl WollCarl Woll

77.9k3102206

answered Apr 30 at 16:14

Carl WollCarl Woll

77.9k3102206

answered Apr 30 at 16:14

Carl WollCarl Woll

77.9k3102206