Revisions to Behavior of Remove inside a Package

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edited Apr 13, 2017 at 12:55

1

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (that means in aPackage` , because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

I'm strongly encouraging to read a very nice answer of Szabolcs:

How symbol lookup actually worksHow symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

? aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

? aPackage`Private`aTestFunction

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (that means in aPackage` , because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

I'm strongly encouraging to read a very nice answer of Szabolcs:

How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

? aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

? aPackage`Private`aTestFunction

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (that means in aPackage` , because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

I'm strongly encouraging to read a very nice answer of Szabolcs:

How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

? aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

? aPackage`Private`aTestFunction

added 18 characters in body

Source Link

edited Apr 11, 2016 at 8:43

Kuba

138.9k
13
297
803

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (that means in aPackage` , because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

You canI'm strongly encouraging to read more ina very nice answer of Szabolcs:

How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

? aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

? aPackage`Private`aTestFunction

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (that means in aPackage` , because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

You can read more in very nice answer of Szabolcs: How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

? aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

? aPackage`Private`aTestFunction

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (that means in aPackage` , because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

I'm strongly encouraging to read a very nice answer of Szabolcs:

How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

? aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

? aPackage`Private`aTestFunction

added 51 characters in body

Source Link

edited Apr 11, 2016 at 8:35

Kuba

138.9k
13
297
803

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (inthat means in aPackage` since, because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in Private`aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

You can read more in very nice answer of Szabolcs: How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

? aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

? aPackage`Private`aTestFunction

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (in aPackage` since the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[].

You can read more in very nice answer of Szabolcs: How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;

?aTestFunction

Information::notfound: Symbol aTestFunction not found. >>

?aPackage`Private`aTestFunction

Shortly:

Here what is going on, aTestFunction was created in aPackage` context, then you've removed it and since the current context is aPackage`Private` the definition of your function is created there.

More precisely:

New symbols are created in current $Context during read time, (1) the existance of aTestFunction between BeginPackage and Begin lines makes the aTestFunction an exported symbol (that means in aPackage` , because the symbol was not found and the current $Context is apackage` ).

After (2) Remove it's no longer there and (3) your definition is read in aPackage`Private` context. But aPackage`Private` is not going to be on $ContextPath or $Context after EndPackage[] so it is not found by ?.

You can read more in very nice answer of Szabolcs: How symbol lookup actually works

BeginPackage["aPackage`"]; aTestFunction::usage = "aTestFunction usage"; (*1*) Begin["`Private`"]; Remove[aTestFunction]; (*2*) aTestFunction[arg_] := arg + 1; (*3*) Protect[aTestFunction]; End[]; EndPackage;