EquationEvaluator 1.2


A REALbasic plug-in for Runtime Mathematical Expression Evaluation

This is both a PPC and a Carbon/OS X Plug-in.

EquationEvaluator is based on Robert Douglas' Macintosh port of Mark Morley's Expression Evaluator (which can be found in DOS code repositories under the name C-EVAL).

This REALbasic version is a plug-in with just one function that takes a string (a mathematical expression) as an argument and returns a double.

Supported mathematical functions include:

Standard Math Functions
+, -, *, /, ^
and % (modulus)

Standard Trig Functions
sin(x), cos(x), tan(x)
asin(x), acos(x), atan(x)
sinh(x), cosh(x), tanh(x)

Other Functions
exp(x) - e to the power of x
log(x) - natural log of x
log10(x) - base-10 log of x
sqrt(x) - square root of x
floor(x) - x rounded down
ceil(x) - x rounded up
abs(x) - absolute value of x

hypot(x,y) -
same as sqrt(x^2 + y^2)

deg(x) to convert x to degrees
rad(x) to convert x to radians

Built-In Constants
pi = pi (~3.1415)
e = e (~2.7182)

Variable Assignment
=



Instructions:

You give the function (called JEE) a string with the expression you would like evaluated, and it will return the value as a double.

The variable assignment feature makes it possible to assign up to 50 variables (each with a name up to 15 characters long). You can assign the variables before you give the expression (as in "x=3, y=2, x+y") or in the middle of an expression (as in "3+(x=4) + x" which should return 11). Or you can have an expression evaluated as part of the assignment, and used later on in another expression (as in "x=3, y=x+2, x+y" which returns 8). Note that if you do the assignment before the expression then you need to follow the assignment with a comma (,) so that the parser knows where the assignment stops and the expression begins.

EquationEvaluator follows the standard math rules for determining which operations go first (multiplication/division before addition/subtraction, etc.). You can also group parts of your expression with parentheses ( "(" and ")" ) if you want to be sure of the order of operations.

Warning: EquationEvaluator does not evaluate scientific (powers of ten) notation. If you try this assignment "x=3E5" (meaning "x=300000"), EquationEvaluator will become confused and will not return the correct value (probably it will return 0). The best solution is to pre-process any strings with scientific notation so that they replace the "E" with "*10^" (so our assignment above would be "x=3*10^5").

Examples:

JEE("7+11*5") returns 62
JEE("sin(rad(45))") returns 0.707 (the sine of 45 degrees)
JEE("hypot(3,4)") returns 5
JEE("x=5.05, y=2, floor(x^y)") returns 25
JEE("theta=pi/3, cos(theta)") returns .5 (the cosine of pi/3)
JEE("x=5, z=log10(x), z") returns 0.69897 (it returns the value of z, which is log10 of 5)

Download:

Download EquationEvaluator here

More:

You can see a review and comparison of all of the runtime expression evaluating options available for RB users on my RB Math Stuff page. Or visit REALbasic's web site at www.realbasic.com


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