Manipulating Symbols and Contexts by Name
| Symbol["name"] | construct a symbol with a given name |
| SymbolName[symb] | find the name of a symbol |
Converting between symbols and their names.
Out[1]//InputForm= |
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Out[2]//InputForm= |
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This gives the symbol x again.
Out[3]//InputForm= |
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Once you have made an assignment such as
x=2, then whenever
x is evaluated, it is replaced by
2. Sometimes, however, you may want to continue to refer to
x itself, without immediately getting the value of
x.
You can do this by referring to
x by name. The name of the symbol
x is the string
"x", and even though
x itself may be replaced by a value, the string
"x" will always stay the same.
The names of the symbols x and xp are the strings "x" and "xp".
Out[4]//InputForm= |
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This assigns a value to x.
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Whenever you enter x it is now replaced by 2.
Out[6]//InputForm= |
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The name "x" is not affected, however.
Out[7]//InputForm= |
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| NameQ["form"] | test whether any symbol has a name which matches form |
| Names["form"] | give a list of all symbol names which match form |
| Contexts["form`"] | give a list of all context names which match form |
Referring to symbols and contexts by name.
x and xp are symbols that have been created in this Mathematica session; xpp is not.
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You can specify the form of symbol names using
string patterns of the kind discussed in
"String Patterns".
"x*" stands, for example, for all names that start with
x.
This gives a list of all symbol names in this Mathematica session that begin with x.
Out[9]//InputForm= |
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These names correspond to built-in functions in Mathematica.
Out[10]//InputForm= |
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This asks for names "close" to WeierstrssP.
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| Clear["form"] | clear the values of all symbols whose names match form |
| Clear["context`*"] | clear the values of all symbols in the specified context |
| Remove["form"] | remove completely all symbols whose names match form |
| Remove["context`*"] | remove completely all symbols in the specified context |
Getting rid of symbols by name.
This clears the values of all symbols whose names start with x. |
The name "x" is still known, however.
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But the value of x has been cleared.
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This removes completely all symbols whose names start with x. |
Now not even the name "x" is known.
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| Remove["Global`*"] | remove completely all symbols in the Global` context |
Removing all symbols you have introduced.
If you do not set up any additional contexts, then all the symbols that you introduce in a
Mathematica session will be placed in the
Global` context. You can remove these symbols completely using
Remove["Global`*"]. Built-in
Mathematica objects are in the
System` context, and are thus unaffected by this.
