Equation parser

Both applets use the same kind of parser. The parser recognizes the following mathematical operations, elementary functions and variables:

-Basic operations: +,-,*,/ and power ^.
-Trigonometrical functions: sin(), cos(), tan(), asin(), acos(), atan().
-Elementary functions: exp(), abs(), sqrt() and log().
-Other functions: abs(), sign().
-Brackets: ().
-Variables:

• DEW1: t, y.
  
• DEWn: t, y0, y1, y2, ..., y11.

-DEWn's components are separated with semicolon: ;.

There must always be an operator between two operands. For example 2t+3y must be given to the program in the form of 2*t+3*y

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