25.5.4  Creating symbols from strings

Variable and function names are symbols, namely sequences of characters, which are different from strings. For example, you can have a variable named abc, but not "abc". The make_symbol command turns a string into a symbol; for example make_symbol("abc") is the symbol abc.

Examples

then:

The variable abc will have the value 3. Similarly for functions:

which is equal to sinπ/4.

Creating arrays of symbols.

The symbol_array command is used for creating multidimensional arrays of symbols.

• symbol_array takes two mandatory arguments and one optional argument:
  • str, a template string for symbol names.
  • dim=n₁,n₂,…,n_m, a sequence of m positive integers.
  • Optionally, purge, the symbol.
• symbol_array(str,dim ⟨,purge ⟩) returns an array with m dimensions n₁,n₂,…,n_m with indexed symbols as elements. Symbols are created from the template string str by appending indices. Template string may contain m instances of the character ’%’, kth of which serves as the placeholder for the kth dimension index. If placeholders are omitted, indices are simply appended in case m=1, while in case m>1 they are separated from str and each other by the underscore (’_’). If purge is given, then the already assigned symbols are purged, otherwise a warning is printed for each such symbol.
• The indices are in accordance with the current syntax mode (they are either 0- or 1-based).

Examples